^p^ MUS. CO.VIP. ZOOL. -J LIBRARY PROCEEDINGS ^^^ ^ ^^^^ HARVARD ^^^"^ UNIvr-^'.TY CALIFORNIA ACADEMY OF SCIENCES FOURTH SERIES Vol. XXXIII, No. II, pp. 255-359; 10 figs.; 5 tables; 23 plates March 30, 19(i(i THE COCHLEAR DUCT OF LIZARDS' By Malcolm R. Miller Department of Anatomy, Uith'etsity of California School of Medicine, cmd Department of Herpetology, California Academy of Sciences, San Francisco, California Drawings by Wayne Emery, Department of Medical Illustration and Technical Assistance by Michiko Kasahara, Department of Anatomy, University of California School of Medicine, San Francisco, California Contents Page Introduction . 256 IMaterials and Methods 257 Observations . 259 A. General Anatomical Features 259 B. General Anatomical Characters of the Cochlear Duct of Certain Reptilian Orders and Suborders 271 1 . Rhynchocephalia 271 2 . Chelonia 2 74 3 . Serpentes 2 74 4. Sauria 278 5. Crocodilia 278 C. Anatomical Characteristics of the Cochlear Duct of Lacertilian Families 278 1 . Iguanidae 278 2 . Agamidae 279 3 . Chamaeleonidae 281 4. Anguidae 281 5 . Anniellidae 282 6. Xenosauridae 282 7 . Helodermatidae 283 ^ This work was supported by United States Public Health Service grants Xos. GM10649-02 and NB- 05532-01. 256 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. Contents (Cont'd) Page 8 . Varanidae 283 9. Lacertidae 283 10. Teiidae 285 11. Gekkota 285 Eublepharidae Gekkonidae Sphaerodactylidae Uroplatidae 1 2 . Pygopodidae 290 1 3 . Scincidae 291 14. Feyliniidae 292 15. Xantusiidae 292 16. Cordylidae 293 17. Dibamidae 293 1 8 . Amphisbaenidae 294 Discussion 294 Relation of the Anatomy of the Cochlear Duct to Acoustical Performance 294 Relation of Cochlear Duct Anatomy to Lacertilian Classification 302 Summary 308 Acknowledgments 309 Literature Cited 309 Note Concerning the Viewing of Black and White Stereophotographs 3 1 1 Introduction The reptiles are not only the first vertebrates with a clearly defined cochlear duct, but also are remarkable in that they have experimented with the cochlear duct and have modified almost all its various parts. Among the reptiles we find differences in the overall size of the cochlear duct, in length, width, and con- figuration of the sound-sensitive cells constituting the papilla basilaris and marked alterations of the limbus, which is the supporting structure of the papilla basilaris. Differences are also noted in the enclosure of the perilymphatic fluid- filled spaces that transmit the sound-pressure waves to the medial aspect of the basilar membrane. The avian cochlear duct is very similar to that found in the crocodiles. The mammalian duct is apparently also derived from a reptilian tyj^e. but is more specialized, elongated, and coiled. The broad general features of the comparative anatomy of the membranous labyrinth of the vertebrate inner ear have been known for some time and have been most comprehensively presented by Retzius (1881, 1884) and more recently by de Burlet (1934). In 1953, Shute and Bellairs, in a study of the cochlear apparatus of certain gekkonid and pygopodid lizards, demonstrated that a de- tailed study of the cochlear duct had remarkable taxonomic implications. Re- cently, Hamilton (1960, 1964), Baird (1960a), and Schmidt (1964) have added "- '^ ' LIBRARY. Vol. XXXIII I MILLER: COCHLEAR DUCT Oh LIZARDS 257 APR 81966 much to the knowledge of the anatomy of the lizard inner ear and Wever ^di^VARD Vernon (1956, 1957, 1958, and 1960), Wever et al. (1963a, 1963b, and l^ft^iVFP^ITY Wever and Peterson (1963), and Crowley (1964) have indicated .something of the various functional capacities of the reptilian cochlea. It is now obvious that detailed studies of the structure and function of rep- tilian cochleae will provide valuable information in the fields (jf bio-acoustics and reptilian taxonomy and phylogeny. The recent studies of Hamilton and Baird {op. cit.) have helped clarify the general anatomical relationships of lizard inner ear structures and the associated anatomical terminology. These studies, as well as those of Schmidt (op. cit.), were done largely by the time-honored and necessarily basic method of making serial sections, and from these, reconstructions. The present approach to the study of the reptilian inner ear is somewhat different in that, in addition to serial sections, the entire cochlear duct has been dissected out of the animal, and its anatomy studied by direct observation of the three-dimensional structure of the intact apparatus. That this is the same approach used by Retzius, in 1884, is apparent if one studies the illustrations of his great work. While he presented the general features of the anatomy of the membranous labyrinth in a variety of lizards (Iguanidae, Lacertidae. Gekkoni- dae, Chamaeleonidae, Anguidae, and Scincidae), he did not report the detailed anatomy of the cochlear duct in these animals. The object of this paper is to describe and illustrate the gross anatomical features of the cochlear duct of lizards. Materials and Methods Since histologic serial sections of the entire posterior cranium are most help- ful in an anatomic study of the vertebrate inner ear, lizards from a number of families were sacrificed by decapitation, the heads fixed in a variety of ways, and after decalcification, embedded in paraffin or celloidin and serially sectioned. After study and reconstruction of serial sections of various lizard inner ears, it became apparent that by careful dissection one could remove the cochlear duct intact from the otic capsule. Trials on freshly sacrificed lizards soon verified the simplicity and great utility of this procedure (see below). Since the present study is not concerned with the histology of the cochlear duct, but is limited primarily to gross structures, details of histologic prepara- tion will not be presented at this time. While tissue from freshly sacrificed animals is necessary for histological preparations, museum specimens provide excellent material for the study of gross anatomical features of the otic capsule and its contained structures. Thus, intact cochlear ducts were removed from both live animals and a large variety of specimens in the herpetological collections of the California Academy of Sciences and of the Division of Svstematic Biologv of Stanford Universitv. 258 CALIFORNIA ACADEMY OF SCIENCES IProc. 4th Ser. It is possible to remove the cochlear duct from a reptile with only minimal damage to the specimen. A three-sided flap, involving little or no damage to head scales, over the otic area of the left side of the head was folded downward exposing the posterolateral aspect of the cranium. Overlying muscle or extensions from roofing bones were carefully dissected away exposing the lateral aspect of of the otic capsule. The tip of a scalpel or a dental drill was then employed to open the otic capsule exposing the sacculus and cochlear duct. The sacculus was usually removed and the auditory nerve transected at its point of emergence through the medial wall of the capsule; then the cut distal end of the nerve was grasped with fine forceps and the cochlear duct lifted free from the cochlear recess. In the great majority of museum specimens, the original preserving alcohol or formalin had penetrated the otic capsule in time to preserve even the cellular elements of the papilla basilaris. In large thick-boned specimens such as Spheno- don, Heloderma, and Aniblyrhynchus, some details were indistinct because the preserving agent could not penetrate the capsule fast enough to completely inhibit autolysis. After removal of the intact cochlear duct, it was stored in 70 per cent ethyl alcohol for further study. The structural details of the cochlear duct were more easily seen if the calcium carbonate crystals were removed from the otolithic membrane overlying the macula lagenae. This was easily accomplished by soak- ing the specimen overnight in a vinegar-alcohol solution. Visualization of the details of the papilla basilaris and its supporting limbus required removal of the lateral wall (vestibular membrane) of the cochlear duct with fine forceps and scissors. All cochlear ducts were photographed in stereocolor and black and white, and scale drawings were made of each specimen. After characteristic family types were established, a professional artist, Mr. Wayne Emery, executed drawings of both the lateral and medial aspects of the cochlea using the actual specimens. For the present study the following measurements were made of each coch- lear duct: the greatest length and width of the entire duct and the limbus, and the lengths of the papilla basilaris and macula lagenae. Measurements were made by means of a calibrated reticule placed in the eyepiece of a dissecting microscope. The length of the papilla basilaris was estimated to the nearest 0.05 mm. and the approximate area determined by tracing the outline of the papilla basilaris on an appropriately ruled paper, and the areal value determined by use of a Leitz planimeter. While the length of the papilla basilaris was determined for all species studied, the area was calculated for a little less than half the number (see table 2). Since the macula lagenae is usually curved, its length could onh^ be very generally estimated. The area was not determined in the present study, for this would have required dissection and conseciuent destruction of the specimens. Vol. XXXIII I MILLER: COL 11 LEAK UiCT Oh LIZARDS 259 In most cases the measurements reported in the tables and j^raphs are based on one specimen only. That measurements from a single specimen do provide useful data was verified by measuring series of adult specimens of Cnernidophorus tigris (25), Xantusia vigilis (20), Mabuya multijasciata (6), Gerrhonotus multi- carinatus (6), and Dipsosaiinis dorsalis (6). In this sampling, no feature of the cochlear duct varied in its measurements more than 15 per cent within one species. In 25 adults of Cnemidophorns tigris varying in snout-vent length from 73 to 105 mm., the cochlear duct length varied from 1.7 to 2.0 mm. (157'^ variation) and the limbus from 1.2 to 1.4 mm. (147). There was no correlation between these measurements and snout- vent length of adult animals. The length (jf the l)apilla basilaris was very close to 0.8 mm. in all 25 specimens. To determine the effect of growth on cochlear duct elements within a single species, seven specimens of Lci()lopis)iia assatiim, ranging from very young (27 mm. snout-vent length) to fully mature animals (53 mm. snout vent length) were studied. Graph 1 (p. 276) demonstrates that the cochlear duct increases approximately 10 per cent in length and the limbus, 15 per cent, but that the papilla basilaris remains essentially the same length during the postnatal growth of a species. To show the relationship between body size and the length of the cochlear duct and the papilla basilaris in those families where sufficient data were available, such information is presented in graph form (graphs 2-7). While most animals used were adult, if a specimen were immature the dimensions of the cochlear duct and its elements might seem out of proportion to other mem- bers of the family. In those families that have but few representatives or where the available material is limited, the above data are presented in table 2 (p. 272). The present study is based on a gross anatomical examination of the cochlear ducts of 205 species of lizards representing 131 genera and 18 families. Repre- sentatives of all living lizard families except the Anelytropsidae, Shinosauridae, and Lanthanotidae were studied. In addition to the lizards, samples of several families of snakes and turtles have been studied and for purposes of comparison, the cochlear duct of a turtle, a snake, and Sphenodon are described and illustrated. Table 1 is a list of material examined. Observations A. General Anatomical Features. The recent excellent studies of Hamilton (1960, 1964) and Baird (1960a) have greatly clarified the general anatomy of the membranous labyrinth of lizards. For ease of understanding general anatomical relationships, schematic representations of the lateral and inferior aspects of the skull and drawings of the entire membranous labyrinth (lateral and medial views) of Xantusia vigilis are presented (figs. 1-4). The cochlear duct (figs. 3 and 4) is the most inferior portion of the mem- branous labvrinth and is connected with the sacculus bv the sacculo-cochlear 260 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. Table 1. List of materials examined. LACERTILIA Iguanidae Amblyrhynchus cristatus Anolis antiquae Anolis biporcatus Anolis carolinensis Anolis copei Anolis cristatellis Anolis eqiiestris Anolis cnpreus Anolis distichns Anolis poly le pis Anolis sallaei Basiliscus vittatus Brachylophus jasciattis Callisaurus draconoides Chalaradon madagascariensis Corythophanes kernandezi Crotaphytus collaris Crotaphytus wisUzeni Ctenosaurtis pectinata Ctenosanrus similis Dipsosaurus dorsalis Holbrookia texana Hoplocercus spinosus Iguana iguana Leiocephalus carinatus Liolaemus pictris Mariguana agassizi Norops auratus Opiums cnvieri Petrosaurus thalassina Phrynosoma coronatum Phrynosoma douglassi Phrynosoma m'calli Phrynosoma modestum Phrynosoma plalyrhinos Plica plica Sauromalus obesus Sceloporus magister Sceloporus occidentalis Tropiduriis albemarlensis (CAS 87102 [S9])i (SU 7473 [154])- (CAS 67165 [65]) (CAS 63340 [66]) (CAS 79146 [58]) (SU 18702 [146]) (SU 14608 [232]) (CAS 87836 [132]) (SU 14571 [151]) (CAS 79287 [77]) (CAS 68086 [93]) (CAS 23)3 (CAS 50135 [133]) (CAS [16]) (CAS 54659 [115]) (SU 18344 [193]) (CAS [18]) (No data, CAS [14]) (CAS [161]) (CAS 69291 [171]) (CAS [163], + 6 specimens) (CAS 31260 [39]) (CAS 93805 [70]) (CAS [162], + 3 specimens) (SU 14611 [159]) (CAS 85249 [99]) (CAS 62604 [90]) (CAS 79376 [98]) (SU 13950 [191]) (CAS 90946 [96]) (CAS 40170 [56]) (CAS 48854 [204]) (CAS 33657 [222]) (CAS 13110 [216]) (CAS 65315 [210]) (CAS 14550 [94]) (CAS [35], + 3 specimens) (CAS [15 and 19]) (CAS [288], + 4 specimens) (CAS 11435 [95]) i-The first number is the California Academy of Sciences, Department of Herpetology cataloRue number of the specimen. The number in brackets is the catalogue number of the cochlear duct which is presen'cd separately in the collections of the Department of Herpetology of the Academy. -Stanford University, Division of Systematic Biology catalogue number. '^ Uncatalogued fresh specimen, cochlear duct only preserved. Vol. XXXIII I MILLER: COCIII.LAR 1)1 CT Oh' LIZARDS 261 Table 1. Continued. Tropic! luus hispidiis Tropidiints peruvianiis Tropidnrus semitaeniatus Tropidiirus torquatus Unia scoparia Urosaunis ornatus Urostrophus torquatus Uta stansbtiriana Xiphocercus valensiennesn .'Xgamid.ae Agama agilis Agama mipta Agama per sic a Amphibolurus barbatus Amphiboliirus miiricatns Calotes versicolor Chlamydosaiirus kiiigii Draco rizali Gonyocephalus grandis Gonyocephalus modes tus Hydrosaurus pustulosus Japalura polygonata Japalura swinhonis Phrynocephalus nejdensis Sitana ponticeriana Tympanocryptis lineata Uromastix loricatus Chamaeleonidae Brookesia superciliaris Chamaeleo bitaeniatus Chamaeleo brevicornia Chamaeleo dilepis Anguidae A nguis fragilis Diploglossus lessonae Gerrhonotus coerideus Gerrhonotus multicarinatus Ophisaurus ventralis Anniellidae Anniella pulchra Xenosauridae Xeunsaurus graudis Helodermatidae Heloderma suspect Km Helodcrma horrid urn (CAS 49413 [102]) (CAS 8090S [10.3]) (CAS 494SS [221]) (SU 9450 [2.36]) (CAS 42119 197]) (CAS .35069 [218]) (CAS 85236 1181]) (CAS [171) (SU 9307 1199]) (CAS 66314 [88]) (CAS 49540 [61]) (CAS 39105 [1861) (CAS [20, 286], + 6 specimens) (CAS 49063 [601) (CAS 39198 [44, 45], + 4 specimens) (CAS 87839 [344]) (CAS [6]) (CAS 53929 [201]) 262 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. Table 1. Continued. Varanidae Varan us niichalis Varamis pimctatus Varanus salvator Varanus species Lacertidae Acanthodactylus cantoris Eremias argiis Eremias guttulata Eremias guttulata Lacerta dugesi Lacerta dugesi Lacerta viridis Lacerta viridis Lacerta vivipara Psammodromus algirus Psammodromus hispanicus Takydromus septentrionalis Teiidae Anadia bogotensis Ameiva ameiva Ameiva aquilini Ameiva undulata Bachia peruana Dicrodon lentiginosus Cnemidophorus communis Cnemidophorus gularis Cnemidophorus hyperthrus Cnemidophorus maximus Cnemidophorus melanosthethus Cnemidophorus ocellatus Cnemidophorus tigris Cnemidophorus tigris Cnemidophorus tigris Kentropyx calcaratus N eusticurus ecpleopus Pantodactylus species Proctoporus unicolor Tupinambis teguixin GEKKOTA Eublepharidae Coleonyx species Coleonyx variegalus Eublepharus species Gekkonidae Aristelliger nelsoni Bavayia sauvagii (CAS 15766 [141]) (CAS 77677 [84]) (CAS 61120 1114]) (CAS [284]) (CAS 865SS [ISO]) (CAS 86904 [188]) (CAS 91601 [51]) (CAS 91599 152]) (CAS 94081 [3]) (CAS 94072 [4]) (CAS [105]) (SU 22995 11061) (SU 18472 11041) (CAS 92431 [53]) (SU 17279 [235]) (CAS 66112 [46]) (SU 8282 [229]) (CAS 7063 [33]) (CAS 39431 [49]) (CAS 68884 [41]) (CAS 93231 [182]) (CAS 94737 [152]) (CAS 58803 [189]) (CAS 34537 [179]) (CAS 8634 [168]) (CAS 46207 [187]) (CAS 39105 [190]) (CAS 49555 [178]) (CAS 88334 [1]) (CAS [12, 13, 2821) (CAS [315-340]) (SU 8330 [1131) (SU 8370 [158]) (SU 17287 [230]) (SU 15813 [234]) (CAS 89669 [100]) (CAS 5637 1101) (CAS [304, 3051) (CAS 86383 11271) (CAS 39418 11341) (CAS 80835 [116]) Vol. XXXIII MILLER: COC/ILLAR DICT Of- LIZARDS 263 Table 1. Continued. Cosymbotus platyitnts Cyrtodactylus annulatus Cyrtodactylus scaber Gecko gecko Gecko japonica Gehyra miitilata Gehyra oceanica Gehyra variegatus Gehyra variegatus Hemidactylus frenatus Hemidactylus garnotii Hemidactylus persicus Hemidactylus turcicus Heteronata binoei Hoplodaclylus granulatus Lepidudactylus lugubris Microgecko helenae Oedura marmorata Oedura robusta Pachydactylus maculatus Phelsuma madagascariensis Phyllodactylus bauri Phyllodactylus elisae Phyllodactylus marmoratus Phyllodactylus muralis Phyllodactylus unctus Phyllurus corniitus Stenodactylus sthenodactylus Teratoscincus scincus Thecadactylus rapicauda Tarentola mauritanica Sphaerodactylidae Gonatodes fuscus Sphaerodactylus argus Sphaerodactylus cinereus Uroplatidae Uroplatus jimbriatus Pygopodidae Aprasia pulchella Lialis burtonis Pygopus lepidopodus Scincidae Ablepharus lineocellatus Acontias meleagris Aulacoplax leptosoma Brachymeles gracilis Brachymeles schadenbergi Brach vmeles tridact vlus (SU 18566 114X1) (CAS 60207 11211) (CAS 845.^2 11181) (CAS 1300, .5011) (CAS 21749 [139]) (SU 9149 11561) (SU 21778 11571) (CAS 76237 [47]) (CAS 76248 [48]) (SU 9545 11471) (CAS 47411 [131] (CAS 86454 [128] (CAS 87114 [354] (CAS 74805 [126] (CAS 47982 [120] (SU 9389 [155]) (CAS 93936 [122] (CAS 75234 [125] (CAS 75671 [137] (CAS 85889 [109] (CAS [302, 304]) (CAS 9745 [124]) (CAS 86352 [110] (CAS 83590 [107] (CAS 73567 [130] (CAS 91356 [108] (CAS 44119 [117] (CAS 84210 [112] (CAS 84648 [119] (SU 8335 [73]) (SU 18114 [1451) (CAS 7122S [111]) (SU 14991 [1491) (CAS 39290 [64]) (SU 13473 [231]) (SU 16223 [198]) (CAS 77655 [34]) (CAS 77659 [206]) (CAS 83798 [81]) (CAS 84188 [225]) (SU 20822 [228]) (CAS 92855 [82]) (CAS 60493 [205]) (SU 19426 [1231) 264 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. Table 1. Continued. Brachymeles vermis Chalcides polylepis Chalcides sepoides Dasia smaragdinum Egernia nitida Egernia striolata Emoia nigra Eumeces elegans Eumeces fasciatus Eumeces gilberti Eumeces obsoletus Eumeces stimsonii Hemisphaeriodon gerrardi Leiolopisma assatHm- Leiolopisma assatum. Leiolopisma guichinoti Leiolopisma noctua Lygosoma laterale Lygosoma lentiginosits Lygosoma verrauxi Mabiiya mabouia Mabuya midticarinata Mabuya multifasciata Mabuya tmdtifasciata Nessia monodactyla Ophiomorus tridactylus Otosaurus cumingi Rhodona fragilis Riopa bowringii Scincus philbyi Sphenomorphus indicns Sphenomorphus quoyi Sphenomorphus variegatus Tiliqua scincoides Trachysaiirus rugosus Tribolonotus gracilis Tropidophorus rivularis Typhlosaurus cregoi Feyliniidae Feylinia currori Xantusiidae Klauberina riversiana Klauberina riversiana Lepidophyma flavomacidatum Xanlusia henshawi Xantusia vigilis (CAS 60721 [220]) (CAS 92389 [2151) (CAS [36]) (CAS 60S00 [69]) (CAS 76612 [76]) (CAS 83931 [101]) (CAS 72238 [142]) (CAS 31899 [38]) (CAS 71S65 [173]) (CAS 89417 [75]) (CAS 71599 [55]) (CAS 21670 [37]) (CAS 76692 [135])-' (CAS 68571 [80]) (CAS [347-353]) (CAS 83856 [79]) (CAS 64036 [54]) (CAS 17997 [78]) (CAS 83737 [214]) (CAS 83738 [212]) (CAS 71454 [89]) (CAS 60435 [74]) (CAS 85672 [68]) (CAS [299], + 6 specimens) (CAS 17164 [207]) (CAS 84674 [143]) (SU 19591 [192]) (CAS 77196 [67]) (CAS 75671 [136]) (CAS 84585 [85]) (CAS 18685 [86]) (CAS 76869 [91]) (CAS 60281 [184]) (CAS no number [7, 81) (CAS 76678 [71]) (SU 13659 [233]) (CAS 62005 [87]) (CAS 85832 [92]) (CAS 55111 [183]) (CAS 43856 [27]) (CAS 43848 [28]) (CAS 66489 [63]) (CAS 64632 [62]) (CAS [21, 22], + 6 specimens) ••It was discovered too late to be incorporated into the body of this paper thai Iho ndiiiiiuil sphaeriodon has been referred to the synonymy of the genus Tiliqua. Heiiii- Vol. XXXIII MIIJJiR: COCHLEAR I)!CT OF LIZARDS 265 Table 1. Continued. CORDYLID.AK Cordyliis cordylus Cordylus jonesii Cordylus polyzonus Gerrhosaurus flavigularis DiBAMID.AK Dibamus ari^Dilrus Amphisbakniuak A mphishaena juUginosa Ripes biponis Blanus cinereus D iplo met poll zariidnyi Rhine lira floridana OPHIDIA COLUBRIDAE Pitiiophh catenifey CHELONIA Testudinidae Gopherus herlandieri CROCODILIA Alligatoridae Alligator mississippiensis RHYNCHOCEPHALIA Sphenodontidae Sphenodon punctattim (su 12086 rissi) (CAS 12901) (CAS 84191 1291) (CAS [5]) (SU 18762 1 8.?]) (CAS 713.56 12271) (CAS 53726 1224]) (CAS 92400 [2261) (CAS 84534 11401) (CAS 14100 1213]) (CAS [291]) (CAS [H461) (CAS [164], + 5 specimens) (CAS [401) duct. The latter usually arises from the posteroinferior aspect of the sacculus, but may be more inferomedial in location in some families (Hamilton, 1964). The cochlear duct in reptiles as exemplified in Crotaphytus wislizeni (figs. 5 and 6) characteristically contains two sensory areas. The macula lagenae usually occupies the anterior and anteroinferior portion of the duct, but fre- quently extends both anterolaterally and anteromediall^^ The macula lagenae is always covered by an otolithic membrane. The papilla basilaris is a sensory area usually occupying a position on the medial wall of the cochlear duct and is usually associated with an overlying tectorial membrane. (Outline sketches showing the lateral and medial aspects of the cochlear duct of Crotaphytus are presented in figures 5 and 6; figures 7 and 8 are cross sections of the cochlear ducts of Hemidactylus and Sawomalus.) The vestibular membrane makes up the lateral wall of the cochlear duct. The medial wall is more complex and in good part is formed of a modified connective 266 CALIFORNIA ACADEMY OF SCIENCES IProc. 4th Ser. Lot. & Post. Semicircular Canals FIG. 2 INFERrOR VIEW Figure 1. Schematic representation of the otic region, Xantu.sia, lateral view. Figure 2. Schematic representation of the otic region, Xantusia, inferior view. Vol. XXXiril MILLER: COCHLEAR DfC'L OE LI/.ARDS 267 Crus Commune Ant. Semicircular Canal Lat. Ampulla ^ Post. Semicircular Canal Sacculus Lot. Semicircular Canal Ant Ampulla Cochlear Duct Post. Ampulla So cculo- Cochlear Duct FIG. 3- LATERAL VIEW Cr U Post. Semicirc Canal Lot. Semicircu Canal Ant. mpulla FIG. 4 - MEDIAL VIEW Figure 3. Left membranous labyrinlh. lateral view, Xantusia vigilis. Figure 4. Left membranous labyrinth, medial view, Xantusia vigilis. 268 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. Neural Limbus Papilla Basilaris Macula Lagenae Limbic Bulge Saccule- Cochlear Duct Postero- Superior ^i/j Basilar j/^ Membrane Triangular Limbus Cut Edge of Vestibular Membrane FIG. 5 - LATERAL VIEW Poste ro- Super ior Short Limbic Recess Limbic Recess of a Gekkonid , "^ 1 Papilla Basilaris Groove for Peri- TkT lymphatic Duct '^J] Macula " .,, ^•.'Fl Lagenae r»^ Antero- inferior FIG. 6 - MEDIAL VIEW FicuRK 5. Cochlear duct, lateral view, Crolaphytus ivisUzeni. FiGURK 6. Cochlear dud, medial \-ie\v, Crolaphytus icislizcni. Vol. XXXIIIl MILLER: COCIII.EAR DfCT Of- l.l/.ARDS 269 tissue coiitaininu aluiiidaiil intercellular suhslaiicc that imparls a l"lc\i|j|c (juality to this portion of the duct. The supportin<,' tissue is thickened where it sur- rounds the basilar membrane and is termed the limbus. The anterosuperior portion ot' the limbus is thicker and larger than the posteroinferior limb and is variously modified and sculptured on both medial and lateral surfaces. Since the auditory nerve is closely apposed to the medial side of the anterosuperior portion of the limbus, it is designated the neural limbus. The lateral surface of the neural limbus may be merely a thin unsculptured plate, be thickened, or may give rise to liplike projections. A tectorial membrane usually arises from the lateral aspect of the neural limbus and overlies the cellular surface of the papilla basilaris. The medial side of the limbus is differently sculptured in large part to ac- commodate the perilymphatic duct and sac which conduct sound-pressure waves through the perilymphatic fluid from the perilymphatic cistern to the medial aspect of the basilar membrane (fig. 9). Hamilton (1960, 1964) and Baird (1960a) prefer a different terminology for the various portions of the perilym- phatic (periotic) system. Until more extensive studies have been made on the homologies of the structures of the perilymphatic system among different verte- brate groups, I prefer to retain the older terminology. In some types of cochlear ducts, the perilymphatic sac is not enclosed by any portion of the limbus along the greater part of the medial aspect of the basilar membrane (figs. 6 | not insert], and 8). In other types of ducts, a considerable extent of the basilar membrane on the medial side may be enclosed by connec- tions between the two portions of the limbus (figs. 6 [insert | , and 7 ). Shute and Bellairs (1953) refer to the enclosed area as a limbic recess and the perilymphatic space, a perilymphatic diverticulum. Hamilton (1964) terms the recess, a jurrow, and that portion of the perilymphatic sac or tympanic scala that extends into this space, an accessory scala. For the present, I prefer to use the terminology of Shute and Bellairs ( 1953 ) . The posteroinferior part of the limbus is not as much modified as the neural limb (figs. 5, 7, and 8). Because of its approximately triangular shape in cross section it is called the triangular limbus. It should be understood that the limbus is one complete structure varying in shape from a saucer-like plate to an elon- gated ovoid, and has in its central portion an opening or hiatus across which is stretched the basilar membrane. Supported on the lateral aspect of the basilar membrane is a thin bar of connective tissue identical in structure to the limbic connective tissue, which in turn supports the papilla basilaris (fig. 7). The limbic hiatus and papilla basi- laris vary in size and shape from small circular or ovoid to large elongate struc- tures. The papilla basilaris may be a simple continuous strip of cells, or may be 270 CALIFORNIA ACADEMY OF SCIENCES IProc. 4th Ser. Vestibular Membrane LATERAL Papilla Basilaris Macula Lagenae Neural Limbus Tectorial Membrane Limbic Recess Papilla Basilaris Supporting Bar of Pap. Bas. MEDIAL Basilar Membrane Triangular Limbus FIG. 7- Hemidactylus (gekkonid ) FIG.8-Sauromalus(iguanid) Cross sections of cochlear ducts Limbic Recess Papilla Basilaris rDuci Perilymphatic^ '-Sac Med. Aperture of Recessus Scalae Tympani Round W Sacculo-Cochlear Duct Window Columella Tympanic Membrane rilymphatic Cistern Cochlear Duct FIG. 9- Diagrammatic anterior view of left cochlear duct & related structures FiGijRE 7. Cochlear duct, cross section, Hciiiidartyliis. Figure cS. Cochlear duct, cross section, Sauroiualus. Figure 9. Relation of peril_\ mphatic spaces to the cochlear duct. Vol. XXXIII] MILLER: COCIILI'.AR DfCT OF LIZARDS 271 divided by a limbic connective tissue bar. The papilla niav als'i be evenly a>n- toured, or one end may be widened |)rodiicin^ a fusiform-shaped structure. That |)ortion of the cochlear duct housing; the limbus, basilar membrane, and papilla basilaris was termed the par.s hasilaris by Retzius (1884). Since the basilar membrane is only a limited |)orlion of this part of the cochlear fluct, I refer to this as the limbic rather than basilar portion of the duct. The anterosuperior part of the cochlear duct is supported alon. ft, «-N <• 00 (J fe; 3 tij o o o o O O -H I I in I d d <^l <^i -^ CO O '-n d> di '^ d> ro ^H o <~^ o o o -+ rH rt ,-H CO oooooo^ooo vD vO vO vO Cv O vO d> d> d> d> di '^ '^ a^ t~- t-~ 'O T-H rvj —I o --■ .-H CO 00 I I I I Tf O t^ t^ vO CO Ov CO t^ Tt -^ vO CO 00 I I I lo O >-i o OOOCCOOOOCOCOr^vO o o o o T-< ^ o o o ^~; ^ vq CO r^i r-1 .— I .-H I I I I Ov Ov O t^ t^l O CS (6 T^ ■^ ■r^ ^ ^^^ r-i .— I O Tf lO --H --H l-H o o o o — o o CO VO -H 'i- Tf \0 Tt- OO CO d ^ lO vO ci o o o o « o o t^ O — I vO d -i — : — ■ r-q i-H (xj ov VO O d> (D ^ rf CO <^1 CO O CO in d d -H ^ (Ni d d rv) T-( ly-) O O :i; _>. -a CHCAitnXuQ > r> HH ^ b<' ^ X X >< l-H I— I k>( k> I— I ■>. p— ( I— I I'N rS v> ■^ ■-> p— I I— 1 v" ?*< ^ > X ^ X X 276 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 1.5 1.4 1.3 1 .1 1.0 or- Cochlear Duct ,jQ >o-o o — o cr*"" / / Limbus \ \. Papilla Basilaris 25 30 40 45 53 (immature) Snout-vent len Gr.aph 1. Changes in the length of the cochlear growth of the scincid lizard, Leiolopisma assatum. gth in mm, (fully mature) duct, limbus, and papilla basilaris during 1. Amblyrluinchus en status 2. Anolis antuiuac Anolis biporcatus Anolis carolincnsis Anolis copei Anolis cristutcllus Anolis cupreus Anolis distichus 9. Anolis equestris 10. Anolis polijlepis Anolis sallaei Basiliscus vittatus Br achy loph us fasc i atus Callisaiirus draconoidcs Chalarodon mudaaascuncnsis Coryi h oph an e s h c rn an dc .:■ 1 1 Crotaphytus collaris Crotaphytus wisliseni 19. Ctcnosaura pcctinata 20 Ctcnosaura similis D I p s s a u r u s d o r s alls Holbrookia tcrana Hoploccrcus spinosus Iguana iguana Lcioccphalus carinatus Liolacmus pictus Mari g u a na a a a s si si Norops auratus 29. Oplurus cuvicri 30. Pctrosaurus thalassina Phrynosoma coronatum Phrynosoma douglassi Phrynosoma m'calli P h r y n o s o m a mode s t u m ,').■?. Phrynosoma platyrhinos 36. Plica plica 37. Suuromalus obcsus 21 23. 24. 2.1 . 26. 27. 28. 31. 32. 33 . 34. Graph 2. Relation between the snout-vent length and cochlear duct and papilla basilaris length in the Iguanidac. Vol. XXXITTl MILLER: COCHLEAR DICT OF LIZARDS 277 2.71- 2.5 2.3 2.1 - 1.9 1.5 1.3 1.1 LI —length of cochlear duct O —length of papilla basilaris Q. m D" D^o Q36 Q37 Qas [e] Q44 [329 47 18 5 320013] 25 840^2 7 39£] [Uli^lCEll Q^8 D^3 D3 .?,9. 4(L D^ ©@ © ©®© :2£®^ O^' 20^44 ^ 27 ^^^ ^ 46 (26) (3^3I^^S^^n ■^^• 34-©^ (^33 ^cy ^Q .See loporus mcufister Sc e loporus occ identa lis Tropidurus albeniarlensis Tropidurus hispidus Tropidurus peruvianus Tropidurus scmitacmatus Tropidurus torquatus Uma scoparia Urosaurus ornatus © Urostrophus torquatus Utu stansluiriana Xiphocercus ralcncicnncsii 1//J I I I I L J I I I I I L_L 40 60 80 100 120 Snout-vent Length in 140 160 Graph 2. Relation between the snout-vent length and cochlear duct and papilla basilaris length in the Iguanidae. 278 CALIFORNIA ACADEMY OF SCIENCES |Proc. 4th Ser. Like Sphenodon, the snake cochlear duct shows incomplete fusion between the lagenar and limbic portions. Whereas in Sphcnodon, turtles, and most lizards, the limbic portion of the cochlear duct is larger than the lagenar, in snakes, the lagenar sac is considerably larger than the limbic area. There is no marked modification of the lateral wall of the neural limbus, and the medial limbic wall shows no extensive recesses. The papilla basilaris is ovoid to slightly elongate and small in its dimensions (table 2). 4. Order Sauria (lizards). In this order I have seen the cochlear ducts of approximately 39 per cent of the living genera (131 of approximately 334 genera), representing 18 families. The most striking feature of the lizard cochlear duct is that it is anatomically distinct for each family and shows considerable modifications of its constituent elements. General anatomical characteristics of the lacertilian cochlear duct are: (a) usually complete fusion between the lagenar and limbic portions; (b) a limbic portion usually equal to or larger than the lagenar; (c) modification of the neural limbus; (d) a papilla basilaris varying markedly in length and shape; (e) a basilar membrane variously open or closed by the limbus on the medial aspect; and (f) except for the skinks, no marked tendency for bending or coiling of the duct. 5. Order Crocodilia. I have seen the cochlear duct of AUigator iiiississip- picnsis. The duct is considerably elongated and has a half turn or twist. The lagenar area is reduced to a small dilation at the inferior tip of the duct. The papilla basilaris is at least twice as long and its surface area is much greater than that of other reptiles (table 2). There are other modifications of the perilym- phatic cistern, duct, and sac but these will not be described in this paper. C. Anatomical Characteristics of the Cochlear Duct of Lacertilian Families. The families of lizards are arranged according to my present concept of an increasing degree of complexity of the cochlear duct, except that T treat the dibamids and amphisbaenids last as their relationships are not clear at this time. 1. Iguanidae (plate I; graph 2). While the iguanids and agamids show many cochlear duct features in common, nevertheless they each possess distinc- tive cochlear features. I believe that the duct types found in the members of these two families are generalized or relatively unspecialized. Features of the iguanid cochlear duct : a. The cochlear duel is i)yramidal in shape, the base broad, and the inferior ti]i usually pointed, although occasionally rounded. Medial bending of the in- ferior tip is not marked, but may be prominent in some species. The duct is not as square as is that of the agamid, and not as elongate as (hat of many other Vol. XXXTIIl MllJ.RR: COCIIl.EAR DJCT Of LIZARDS 279 faniilirs (see length-widlh ratios in table ?)). The length of the ( oc lilcar duct varies directly with the snout-vent length of the si)ecies (grajih 2). b. The macula lagenae is large, begins high anterosuperiorly, and runs down the anterior surface of the duct, and at its inferior extremity curves medially. The macula lagenae is two to three times the length of the papilla l)asilaris. c. The limbus is ovoid to morlerately elongate. Klongati(jn is more marked in the anolids. The neural limbus has a moderate bulge on its lateral face that is bar- or rolling-pin-like in appearance. In the tropidurid iguanids, the neural bar is more undercut than in other iguanids, a feature similar to the agamid lateral neural limbus. (1. In most species, the anterior edge of the duct has only a shallow groove for the perilymphatic duct, while in large species with large ducts, the perilym- jihatic duct groove is deepened. e. The medial aspect of the basilar membrane is almost entirely open, but in some species short shallow limbic recesses are present both superiorly and inferiorly. The medial limbic flanges housing the auditory nerve and perilym- phatic duct are not prominent. f. The papilla basilaris is relatively short but increases in length and area in the anolids (table 2 and graph 2). There is not as close a correlation between species size and papilla basilaris length as there is in some other lizard families (compare graphs 2 to 8). The length of the papilla basilaris therefore is prob- ably associated with specific differences other than that of size. While a detailed analysis of generic differences will be reported in a later paper, a few general observations are noted here. Compared with other iguanids, the limbus and papilla basilaris is longer in anolids; the cochlear duct is more pointed and elongated, and the neural limbic bar better developed in the tropi- durids and in Plica plica; the neural limbic bar is more prominent in Sauromalus obesus; and the limbus and papilla basilaris are relatively short and small in the "earless" lizard, Holhrookia fcxaiia. 2. Agamidae (plate TI; graph 3). a. The cochlear duct is nearly as broad as long and is shaped like a right triangle with the right angle at the posterosuperior corner. The inferior tip is rounded and blunt. There is some correlation between cochlear duct and papilla basilaris length and species size, but there is not as close a correlation as is found among genera in other families. b. The lagena is relatively large and the macula lagenae two to three times the length of the papilla basilaris. c. The lateral side of the neural limbus is thickened giving rise to a promi- nent bar which is more pronounced than the type found in the iguanids. but not as marked as that of the anguids, lacertids, or teiids. The triangular limbus is flared posterosuperiorly. 280 CALIFORNIA ACADEMY OF SCIENCES IProc. 4th Ser. CO 1 A — U 40 60 80 100 120 140 160 Snout-vent Length in mm. Graph .v Relation between the snout-vent length and cochlear fluct and papilla basilaris length in the Agamidae. Vol. XXXIIII MII.I.I'.R: COCHLEAR Dl ( I oh l.l/.ARDS 281 (1. The f^roovt' for llic pt rilyiiiphatk dint \arii's from shallow to Hcep. beinj^ deeper in large species with larger and more stoutly constructed ducts. e. The medial face of the basilar membrane is mostly unenclosed, but there are short supt'rior and inferior limbic recesses. The medial limbic flanges are not prominent. f. 'Yhe papilla basilaris is relatix'ely short, either elongate or fusif(jrm. and the enlarged end superior in location. The papilla varies from 0.2 mm. to 0.4 mm. in length; there is some tendency for it to be longer and greater in surface area in larger species (graph 3 and table 2). While the number of agamid genera so far studied is not large, there is a tendency for the shape of the lagena to vary from genus to genus; in Sifana pontkeriana, the lagena is reduced in size, in Tympanocryptis lineata, the an- terior edge of the cochlear duct, instead of being curved, is straight and set at an angle of 45 degrees to the papilla basilaris. And while a blunt or rounded inferior tip is an agamid characteristic, in Ai^aiiia pcrsica (but not Ai^auia agilis or Agama nupfa), the tip is pointed. 3. Chamaeleonidae (plate III). a. The cochlear duct is characteristically triangular, the length approxi- mately 25 per cent greater than the width. The lagenar and limbic portions form a single unit showing no tendency to separation. b. The macula lagenae is moderate in size. c. The limbus is thin and saucer-like in shape. The lateral side of the neural limbus shows only the slightest elevation. The limbic hiatus is relatively large and is circular in outline. d. The groove for the perilymphatic duct is definite but shallow. e. The medial aspect of the basilar membrane is open. f. The papilla basilaris is small and circular to slightly ovoid in shape. There is no indication of variation in papilla size with species size (table 2). An in- sufficient number of species have been studied to know if there are intrafamilial differences. 4. Anguidae (plate IV). a. The cochlear duct is moderately elongate. b. The lagenar part of the cochlear is moderate in size and the macular length about twice that of the papilla basilaris. c. The limbus is ovoid and the central hiatus of good size. The lateral side of the neural limbus shows a prominent projection which is longer than the papilla. The neural limbic projection is much more prominent than that found in the iguanids or agamids, but not quite as well developed nor as shelf-like as that of the lacertids. Because of the development of very elongate bod\- types in the anguids, it is difficult to correlate species size with cochlear duct dimen- sions. 282 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. d. The medial side of the limbus has two quite prominent flanges which partially house the perilymphatic duct. This feature is best developed in the gerrhonotids. e. The medial face of the basilar membrane is mostly open, but there are short inferior and superior limbic recesses. f. The papilla basilaris is elongate and modest in its dimensions. In most species there is a small area at the inferior extremity of the papilla that appar- ently lacks hair cells. In both Ophisaurus vcntralis and Anguis jragilis, the total length of the cochlear duct as well as the length of the macula lagenae and the length and area of the papilla basilaris are relatively small (table 2). This is probably the result of regression or degeneration. 5. Anniellidae (plate V). a. The cochlear duct is somewhat square in shape. b. The lagenar area is reduced in relation to the limbic portion, and it is probable that the cochlear duct has been shortened largely by a decrease in the dimensions of the lagenar area. c. The limbus is thin, concave, and eccentrically ovoid. The limbic hiatus is quite large which may be characteristic of either a primitive or a reduced condition. A small bar-like limbic lip forms the anterior edge of the neural limbus. The relative distance of the lip from the papilla basilaris gives the appearance that the neural lip has been displaced in position. d. The groove for the perilymphatic duct on the medial side of the cochlear duct is narrow and shallow. e. The medial aspect of the basilar membrane is small and entirely open. f. The papilla basilaris is ovoid and small (table 2). 6. Xenosauridae (plate VI). a. The cochlear duct appears tall because of the relatively large area above (anatomically dorsal to) the limbus proper. Measurements of the cochlear duct show it to be approximately equal in length and width. b. The lagenar area is mildly constricted from the limbic portion, a possible result of degeneration of the limbus in this family. The macula lagenae is of moderate size and extent. c. The limbus is relatively small and almost flat on its lateral face except that there is a moderate elevation at the anterior border adjacent to the lagenar portion. There is no apparent modification of the neural limbus. d. The groove for the perilymphatic duct is quite deep both anterosuperiorly and on the medial surface of the duct. e. The medial face of the basilar membrane is open. f. The papilla basilaris is very small (table 2). Vol,. XXXIIII MILLER: COCII Ll:.\ l< 1)1 CIOII.I /.\ RI)S 283 7. Ilc'l<)(i('riiia(i(l;if ( |)l;ilc \ 1 1 ). a. The cochlear duct is trianuulai-, and \\\c limbic poition (|iiilc lar^e. I). The la^enar area is less tliaii Ihc liiiilii( . hiil the hkk ula la^^enae is of ntoderale proportions. c. The linil)iis is (|uite tliick. The neural linil)ns presents a rounded promi- nence that is more massive than the iguanid lip, and different from tlie an.L'uid in not bein,u; sharply undercut just al)ove the basilar membrane. d. and e. The groove for the ])erilymphatic duct and sac is large and shallow and the medial aspect of the basilar membrane mostly open. A short liml)ic recess is present at the superior end of the basilar membrane. f. The papilla basilaris is proi)ably elongate (my specimen was not perfectly |)reserved): it is longer than that found in either the anguid or iguanid lizards (table 2). The nerve supplying the papilla basilaris is bifid, but the papilla does not appear to be divided into two segments. 8. Varanidae (plate \'III). a. The cochlear duct is large and elongated (approximately twice as long as wide) ; the greater length is due to the large, heavily constructed limbus. b. The pars lagena is of moderate proportions and the macula lagenae a wide strip covering the anterolateral, anterior, and anteromedial aspect of the lagena. c. The limbus appears massive and may have a small narrow central bridge dividing the limbic hiatus into two unequal portions. The superior end of the divided hiatus is about twice the length of the inferior portion. In specimens with an undivided hiatus, there is a narrowing of the hiatus in the same area where it is divided in others. Two of my four specimens have a divided hiatus and papilla, and two do not. The lateral face of the neural limbus does not show a definite projection, but is thickened in its midportion above each part of the divided limbic hiatus. d. The groove for the perilymphatic duct is quite deep. e. The medial face of the basilar membrane is about two-thirds open: a superior limbic recess covers the upper half of the superior portion of the mem- brane, and a shorter inferior recess covers only 5 to 10 per cent of the inferior part. f. The papilla basilaris is elongate and may be divided into two unequal portions; the superior part is about twice the length of the inferior. The papilla may or may not be divided. The length of both the cochlear duct and the papilla basilaris is directly related to the size of the species (tal)le 2). 9. Lacertidae (plate IX). a. The cochlear duct is characteristically triangular and the limbic portion markedly posterior (caudal) as well as superior in position. b. The lagenar portion of the cochlear duct is relatively large and has a 284 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. CO Q. O 0- O u 1. Acanthudactylus cantons 2. Eremias argus 3. Eremias guttulata 4. Lacerta duqcsii 5. Lacerta viridis 1.3 6. Lacerta vivipara 7. Psammodromus alqirus 8. Psammodromus hispanicus 9. Tachydromus septentrionalis |~| —length of cochlear duct Q —length of papilla basilaris 20 40 60 80 Snout-vent Length in mm. 00 Graph 4. Relation between the snout-vent length and cochlear duct and papilla basilaris length in the Lacertidae. long superior-inferior axis and tends to extend more superiorly than it does in other families. The macula lagenae is correspondingly long, courses down the entire anterior border of the duct, and extends onto the inferior medial wall. c. The limbus is ovoid-elongate and characterized by a medial bar or bridge dividing the limbic hiatus into two approximately equal halves. The neural lip is a prominent ridge more marked than that of the anguids, but not as well de- veloped as that of the teiids (compare plates IV, TX, and X). d. The groove for the perilymphatic duct is shallow. Vol. XXXIII I MILLER: COCHLEAR 1)1 CT OF LIZARDS 285 e. The medial face of the hasilai' mciuhraiic is nol enclosed and liie excava- tion for the perilymphatic sac relatively deep. Very short superior and inferior limbic recesses are present. f. The papilla basilaris is di\ided into two almost e()ual portions. Kach part is slij2;htly fusiform but elongate in shape. The |)apilla basilaris is both fairly short in length and small in area and seems to vary directly with species size (table 2 and graph 4). Among the lacertid genera studied, there are minor variations in the thickness and shape of the limbic lip. and the exact shape of the lagena. 10. Tciidac (plate X). a. The cochlear duct is elongate. I'he posterosuperior curve of the limbus projects dorsally and more superiorly than the corresponding lagenar edge. The inferior tip of the duct is pointed and curves sharply in a medial direction. The teiid cochlear duct has expanded both superiorly and inferiorly; the teiids therefore, differ from the gekkonids, in which group the duct expands superiorly, and from the scincids where the duct expands inferiorly and medially. b. The lagenar portion of the duct is large and well developed; it forms a robust anterior edge. The macula lagenae is always longer than the papilla basilaris. c. The limbus is one of the most elongate found in the lizards, the length, width ratio being 46 per cent (table 3). The limbic hiatus is long and narrow. The lateral face of the neural limbus has a rather heavy umbrella-like projection in the middle 50-60 per cent of its length. The neural limbic lip is considerably shorter and much less delicate and projecting than that of the Gekkota and pygopodids. d. The groove for the perilymi)hatic duct is not well marked. e. The medial face of the basilar membrane is not enclosed and receives a widely expanded perilymphatic sac. f. The papilla basilaris is moderately long and varies in length and area wdth the size of the species (table 2 and graph 5). The papilla is slightly expanded inferiorly, and narrowed superiorly. There is usually a break in the papilla basilaris toward the superior tip and the papilla is thus unequally divided with a very short superior portion barely separated from a much longer inferior strip. There is no limbic bridge, however. The tendency towards division of the papilla, together with the development of a thick umbrella-like limbic lip and an open medial basilar membrane are conditions very similar to that found in the lacertids. Most teiids have robust cochlear ducts, but the microteiids {Anadia, Bachia, Pantodactylus. and Proctoporus) show considerable reduction in both the limbic and lagenar portions of the duct. 11. Gekkota (including Gekkonidae, Eviblephaiidae, Sphaerodactylidae, and Uroplatidae) (plate XT; graph 6). 286 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. o U 3.4 y ^ 2.6 2.4 2.2 2.0 D— length of cochlear duct Q-length of papilla basilaris m [U s - © © a [HE Aniciva amciva 2. Ameira aquilini 3 Amciva undulcita 4 Anadia hoqotcnsis ,K Bachia peruana 6. Cncmulophonis comminus 7. Cnemidophorus cnilaris 8.. Cnemidophorus hyperthrus 9 Cneinidopliorus maximus © o © Cnemidophorus melanostcthus Cnemidophorus tigris Dicrodon lentiainosus Kcntropyx calcaratus Neustic2irus ecpleopus Pantodactulus sp. Proctoporus unieolor Tupinambts feauiiin I I I I I I 30 50 70 90 110 130 Snout-vent Length in mm. 150 Graph 5. Relation between the snout-vent length and cochlear rluct and papilla basilaris length in the Teiidae. Vol. XXXIII 1 MILLER: COCHLEAR /)[(/' OF LIZARDS 287 00 U F ^ 2.8 2.6 2..1 - 2.2 2.0 /. Arislcllidcr iiclsinii .?. ^iarui/ia sduiddii 3. Colcomix s'P. 4. Cosi/mholus plain urux :') . Cvrlodachilus annulalus EH 1.2 ^ B3 E] H "life] E00 © - H © © © - Qas © @ © [322 -'□¥fe] B© © © ^ -0© ©3 - © 0© © 30 1 2^18 22 a. 7. 8. 9. 10. 11. 12. 13. 14. iri Ifi 17 i.v, 19. 20. 21 . 00 23. 24. 2:'). 26 27. 28. 29. 30. 31. 32 33. 34. J \ LJ L n —length of cochlear duct O -length of papilla basiloris [334 Cyrlixlavhilus s caber Eublepharis macularius Gecko japonica Geliyra mutilata Gehyra oceanica Gehyru vaneqala G una I odes tuscus Hemidactylus f renal us Hemidactylus ciarnotii H e VI i d a c tylu s p e r s i c u s Heleronata binoei Hoplodacty Ins gran u latus © ©34 Lepidodaclylus luaubris Microgecko helenae Oedura mar moral a Oedura rohiisla Pachydacly lus maculatus Phyllodactylus bauri Phyllodacty lus e lisae Phyllodactylus marmoralus Plu/llodaclylus jnuralis Phyllodactylus unctus Phyllurus cornutus Sphacrodacty lus argus Sphaerodactylus cinereus Stenodactylus sthenodactiilus Teratoscincus scincus Thecadacty lus rapicauda Uroplal us iimbriatus _1_J I I I 30 50 1 10 30 150 170 Snout-vent Length in mm. Graph 6. Relation between the snout-vent length and cochlear duct and papilla basilaris length in the Gekkota. CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 3.8 p- 3.0^ CO 2.8 2.6 2.4 2.2 2.0 1.8 ^ Q38 .Q Q -length of cochlear duct Q— length of papilla basilaris D30 Q 1.6 o U 1.4 1.2 1.0 D40 35-FTol [9] Q34 038 s © |T3|[37] 27 — 32t |l9| l3 ©5© D23 □ 24 I tD36 © © © ^T, 22 ill I 6 18 (5 ) © ^t ^Si 36© (3(^37 Cy^ (fsT 29 33 © D^a [H 20 31 VIII L © ^ 43-^24 (23) ©2B © Q42 ©^ '-0 Va 20 40 60 80 100 120 140 160 180 310 Snout-vent Length in mm. Graph 7. Relation hi'twcun the snout-vcnl k'lijith and cochlear duct and pai)illa basilaris length in the Scincidae. Vol. XXXTin MILLER: COCHLEAR DUCT OF LIZARDS 289 /. Ahlcpharus liiicnvcllalus 23 2. Acontias mclcagns 24. 3. Aulacnpla.r IcptosDUia 2') 4. Brachymeles gracilis 26 ■'). Brachj/mclcs schadcnhcrai 27. nraclnniiclcs tndachi lus 28. Chalculcs poli/lcpis 29 Chalcidcs scpoidcs 30. Dasia smaragdinum 31 .. Egernia nitida 32. Edcrnia stnolala 33. Emoia nigra 34 13. Eumcccs clcgans .7,7 14. Eumeces stimpsonii ,75" 1'). Eumeces gilbcrti 37, Eiuneces obsulctu.^ 38. Eumeces fasciatu.s J9, Hemisphaerodon acrrardi 40. Leiulopisma assatum 41 20. Leiolopisma guichinoti 42. 21. Leiolopisma noctua 43. 22. Li/aosoma latcralc 6. 7 - 8. 9 10. 11 . 12. 16. 17. 18. 19. L]l gosom a hnluiin os u s Liigosoma rcrruu.vi Ma buy a mabouia Ma buy a mullifasciata Mabui/a muUicarinata Ncssia monodactyla Ophiomorus Iridactylus Olosauru.s cumingi Rhodona iraailis Riopa bowriiKiii Sc Ulcus phi I by I Sphcnomorphus indicus Sphenomorphus guoyi Sph en om orpli u s I en u i s Sphenomorphus variegalus Tiliqua scuicoides Trachysaurus rugosus Tribolonotus gracilis Tropidophorus rivularis Typhh)saurus cregoi ( Eeyliniidae I Fey lima eurrori Gr.-\ph 7. Relation between the snout- length in the Scincidae. vent length and cochlear duct and papilla basilaris ^ —Length in a specimen of 60—70 mm. snout-vent length -^ ■^f- ■^ J I I ' I I I .2 1.6 2.0 _l 2.4 Mi 1 1 imeters Graph 8. Range in length of the papilla basilaris in lizard famihes. 290 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. So far I have not studied a sufficient number of eublepharids and sphaero- dactylids to state whether they differ significantly from the gekkonids in cochlear duct characteristics. For the present, I will discuss the Gekkota as a whole. a. The cochlear duct is relatively large and heavy in appearance. The limbic portion has expanded in a posterosuperior direction and pushed into the saccular area. The pars lagena is also prominent and occupies the anteroinferior portion of the duct. The general form of the duct is elongate, and the inferior tip some- what pointed. b. The large macula lagenae lies at an angle of approximately 30 to 40 degrees to the papilla basilaris, whereas in the lacertid-teiid complex, the macula lagenae lies more nearly parallel to the papilla. The most notable difference between the basically similar gekkonids and pygopodids is that the macula lagenae and papilla basilaris are parallel to one another in the pygopodids. (Com- pare plates XI and XII.) c. The limbus is large and ovoid-elongate (table 3) and its most outstanding feature is the extension from the neural limbus of a thin awning-like projection curving out over the papilla basilaris. This lateral neural limbic projection is much thinner and more delicate as well as relatively greater in extent than the teiid and lacertid limbic lips. d. The anteroinferior edge of the cochlear duct is frequently deeply grooved by the perilymphatic duct. e. Only the inferior third of the basilar membrane is open medially as a long limbic recess houses the superior two-thirds of the membrane. f. The papilla basilaris is an elongate slightly fusiform structure. The thicker end lies inferiorly and there is no tendency for the papilla to be divided. The length and area of the papilla usually varies directly with the size of the species (table 2 and graph 6). There is less variation in the cochlear duct of the Gekkota than in any other group of lizards. In fact, the constancy of anatomical detail is remarkable. Only in very small species such as Heteronata binoei, Microgccko helenae, and Sphaerodactylus argus is the size of the lagenar and limbic areas much reduced. The reduced size of the limbus and lagena in these small species results in a miniaturized and not a degenerate structure. The cochlear duct of Uroplatus jimbriatus differs only in having a somewhat enlarged lagena. 1 2 . Pygopodidae (plate XII ) . a. The pygopodid cochlear duct is very similar to the gekkonid duct in that it is elongate, heavy, and superiorly expanded. It differs from the gekkonid duct in that the macula lagenae is more parallel to the [lapilla basilaris. Also, the inferior tip of the pygopodid duct is more rounded. An insufficient number of pygopodid species have been studied to determine cochlear duct and species size relationships. \(.i.. XXXIII I MlLIJiR: COCHLEAR DrCT Oh /.//.AMDS 291 I). While in the ,ut'ki<()ni