B R A MAR 18 1985 11 sen 111 of Coiiipan^J^V^^QZooIogy us ISSN 0006 9698 ■'^•iTY Cambridge, Mass. August 15, 1980 Number 463 JAW MUSCULATURE OF THE WEST INDIAN SNAKE ALSOPHIS CANTHERIGERUS BROOKSI (COLUBRIDAE, REPTILIA). Kenneth V. Kardong^ ABSTRACT The West Indian colubrid snake Alsophis cantherigerus hrooksi is presently assigned to the subfamily Xenodontinae (sensu Maglio, 1970). It is a member of an assemblage of related snakes from continental stocks that have spread to and diversi-fied within this Caribbean archipelago. The head myology proves to be representa-tive of other xenodontine snakes of the West Indies and thus is a con\ enient reference for comparison to other subspecies and may be useful in later comparisons to other species' assemblages of the region. Its jaw musculature conforms basically to that of other generalized colubrid snakes. Special attention is given to the internal fascicular bundles within each muscle. The adductor mandibulae externus superficialis passes posteroventrally from its origin on the skull, inserting mostly by a broad aponeurosis except, for a rostral slip that forms its anterior edge and inserts directly on the mandible. The adductor mandibulae externus profundus consists of anterior and posterior wedges of muscle delineated by a vertical suture between them. Adductor mandibulae externus media-lis is separable into superficial and deep slips. One significant difference in general muscle anatomy from some other colubrids concerns the protractor quadrati. This muscle inserts on the retroarticular process of the mandible which differs from the genus Opheodrys in which it is reported to insert on the quadrate. Lateral jaw musculature proves to be very similar within the subspecies of A Isophis cantherigerus. The only detectable difference occurs in the deep division of the depressor mandibulae. In most subsptCMS (adspersus, brooksi. cantherigerus. cayma-nus. schwartzi), this deep division is a single slip of the depressor arising from a single site. However, in fuscicauda, pepei, and ruttyi it splits lengthwise so as to arise from two sites of origin. One instance of individual asymmetry was identified in adspersus wherein the insertion of the superficialis differs on left and right sides. The conformity of lateral jaw musculature among subspecies related to hrooksi emphasizes the uniform nature of this group. Other authors also found this unifor-mity in features of the integument, skull osteology, and hemipenial characteristics. 'Department of Zoology Washington State University Pullman, Washington 99164
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