332 PROCEEDINGS OS THE ACADEMY OF have scarcely any species in common with the shells of San Diego, while in general they agree with those of the West American tropical fanna. They are more nearly related to those of Acapulc6 and Panama than to those of Mazat-lan, although in the same latitude on the opposite side of the Gulf. The presence of such shells as Oniscia tuberculosa, Cassis coarctata and abbreviata, Lathirus castaneus, Oliva porphyria, Columbella hcemastoma, Conus princeps, &c, Several of which are also found at Guaymas, though not at Mazatlan, distinctly points to far more tropical conditions than could have been expected in so high a latitude. The Trochidce, Patellidce, and similar intertidal families, however, bear more near relationship to the shells of Mazatlan; while a. soli-tary, though fine and apparently fresh specimen of Haliotis splendens, entirely unknown in the Gulf, serves as a connecting link to the fauna of Lower Cali-fornia. Catalogue of the Venomous Serpents in the Museum of the Academy of Natural Sciences of Philadelphia, with notes on the families, genera and species. r>Y E. D. COPE. In the cephalic vertebra of the typical venomous serpents, we observe the greatest modifications of the archetypal vertebra, in the ophidian order. This, which is most excessive in the inferior arches, consists in First, the great shortening and thickening of the haemapophysial element of the nasal vertebra, (superior maxillary,) to serve as a firm foundation for the long curved venom fangs. Second, its ginglymoid articulation with its neurapophysis (prefrontal), by motion, upon which the fangs are erected or depressed, and Third, the great lengthening of the pleurapophysial element of the frontal vertebra, (the tympanic bone), which, acting as a fulcrum, gives the greatest mobility to the articulated pterygoid appendage, the ectopterygoid, and conse-quently to the superior maxillary. Thus, it is evident that this modification has immediate reference to the complete specialization, and more perfect exercise of natural functions, the apprehension of living prey, and its subsequent deglutition. From the possession of these attributes of high organization, we infer that nature has assigned to the typical venomous serpents the first place in the category of ophidians. Hence, also, in attempting to define them as a natural group, we look to those points of structure whence we deduce the evidence of superiority. In the Colubriform venomous serpents, the hsemapophysis of the nasal vertebra still falls considerably short of its hsemal spine, and is much thick-ened in a vertical direction at its distal end, to give a firm support to the fangs. But a tendency to revert to the ordinary ophidian type is seen in its posterior elongation, its oblique articulation with the shortened ectopterygoid appendage, and its imperfect articulation with the neurapophysis. In conse-quence of this structure, the external pterygoid muscle plays upon the maxillary bone at a disadvantage, having, in point of fact, but little power to effect the depression of the fangs. The pleurapophysis of the mandibular arch is shortened. The result of this is, that the pterygoid, articulated to a shorter fulcrum, cannot be drawn forward by the spheno-pterygoid muscle to so great an extent ; hence much less mobility is given to the dependent ectopterygoid and superior maxillary. Of this group genus Naja, (Laur.) offers a typical example ; of the first, Crotalus (Linn). Nowhere have we a more conclusive example of the futility of attempting to define higher groups by external characters alone ; for, in respect to these, the groups, in question, blend in a manner beyond the possibility of satis-factory separation. There are, indeed, external peculiarities', which are highly characteristic of each. On the one hand there are the depressed, scaly head ; [Dec.