252 BULLETIX 15 4, UNITED STATES XATION"AL MUSEUM 



dylus, IfMsa^ etc.), the acquiring of keeled ventral plates {Ken- 

 tropyx, Lefosoma), and the assumption of an unusually small 

 maximum size {Micrahlepharls^ etc.). For obvious reasons, these 

 genera are to be regarded as the specialized Teiidae. The remain- 

 ing genera, which we may speak of collectively as the lower Teiidae, 

 possess longitudinally compressed or conical teeth, five digits, well 

 developed limbs, normal lizard-like form, eyelids, ear openings, 

 large prefrontals, and small dorsal scales, large and smooth ventral 

 scutes and either a moderate or a large maximum size. 



Of those lower teiids, two distinct groups are evident: (1) Those 

 with the tail essentially bicarinate superiorly, and (2) those with a 

 normal rounded or cyclo-tetragonal taiL The first group, evidently 

 in ancient branch of semiaquatic habits, is composed of Dracaena, 

 NeusticuQ'us^ EcMnosaura^ and Crocodihirus. The second grouj:), 

 presumably the one that has given rise to the specialized Teiidae, is 

 composed of Callopistes, Tupinamhis and Ameiva. Callopistes has 

 a high number of longitudinal series of ventral plates and attains 

 a large maximum size like Ttvpinamhis^ but is specialized by the 

 breaking up of many of the large head shields, particularly the 

 anterior ones, and by the assumption of an arrow-headed shape to 

 the tongue. Tu^pina^iibiS shows little specialization and may be de- 

 scribed as a large, overgrown Atneiva^ which differs merely in the 

 constant possession of a higher number of longitudinal series of 

 ventral plates, a characteristic exhibited by the remaining member 

 of Group I, Callopistes^ and by the least specialized genera of Group 

 II, Dracaena and CrocodiJurus. Unlike Tiiipinambis^ the three last- 

 mentioned genera show other notable variations from Ameiva and 

 this, in turn, suggests a more remote relationship. It is Tuphiambls, 

 then, that has apparently given rise to Ameiva and the more s])e- 

 cialized Teiidae. In support of this view, there is some evidence in 

 the fossil record which indicates that the Tupinamhls-Amei'va stock 

 is very ancient, and therefore jDresumably primitive. Camp, a lead- 

 ing authority on the classification of the lizards, has written (1923. 

 p. 316) that "Ambrosetti (1897) and Kovereto (1914) have examined 

 remains of large teiids, close to the living Tupinatiibls^ from 

 Oligocene and Pliocene localities in Argentina. The systematic de- 

 terminations are quite convincing.^- In addition, the absence of 

 C riemidophoi^s and the specialized Teiidae from the Greater Antilles 

 on the one hand, and the wide-spread presence of Ameiva there on 

 the other, seems to argue in itself in favor of the earlier origin of 

 the latter form and its progenitors. Therefore, because of its close 

 i-elationship to Ameiva^ C nemidophorus occupies an intermediate 



^^Althoush Williston (1925) listed the extinct North American Vhamops as a teiid 

 seiuis, Camp (1!)2;5, p. 31G) assigned it to the Iguanidae. 



