CROCODILIANS, LIZARDS, AND SNAKES. 



219 



2. True pr;vaiial or femoral pores, at least in the males. 



Body depressed; tympanuui distinet; femoral 



and pneanal pores Amphiholurus Wagler. 



Body depressed; tympanum hidden, 



Tynqyanocryptis Peters. 

 Body slightly depressed; no femoral pores, 



Diporophora Gray, 



Body compressed; toes denticulated laterally, 



Physignathus Cuvier. 



Body slightly compressed; neck with a large 



frill-liko expansion Chlamydosaurus Gray. 



Body compressed ; toes lohate Lophura Gray. 



Body depressed ; no pr;eanal pores, 



lAolepift Cuvier. 

 AA. Incisors united into one or two large cutting teeth; tail short, with whorls 

 of spines. 



Femoral and prieanal pores. . Uromastix Merrem. 



No true jiores Aporoscelis Boulenger. 



II. Mouth very small; teeth in the upper jaw horizontal, directed iuward; body 

 covered with largo spines Moloch Gray. 



No geuus of AgamidiX' is found iu America, where the Ignaiiida? repre- 

 sent them. The two families i)reseiit some interesting parallels, which 

 show the effects of identical causes iu i)roducing similar effects on the 

 orgaTiism. These parallels are seen in the depressed form of the ter- 

 restrial forms in both families and the relatively compressed form of 

 the arboreal types. In both families the former have representatives 

 with horny imjcesses on the head and on the scales of the body; and in 

 both are types with horny spines on the tail. Among arboreal forms 

 we lind genera of both families with series of horny processes forming a 

 median dorsal crest, and in others a prolongation of the spines of the 

 dorsal and caudal vertebrse, producing a like result. 



Ahdoniinal rilm. 



Iguanid.e. 



Polyclirus. 



Agamid^. 



No abdominal ril)8. 



Ribs greatly prolonged into a lateral wing. 



* * Draco. 



Ribs not ])r()louged. 



Arboreal types, generally comjiressed. 



A dorsal and caudal tin supported by bony rays. 



Basiliscus (no fern, pores). Jjophura (pores). 

 No vertebral fin. 



No femoral pores. 



Form slender, scales in Calotes. ^ 



e<|ual series. Bronchocela. S 



Form elongate; eyebrows 



elevated, tail compressed. Gonyocephalus. 



Form stouter, scales less 



regular. Hypsibates. 



Femoral pores. 

 Low cresttid ; small hyoid 



disk. Brachylophus. 

 High crested; large hyoid 



disk. Iguana. 



jTail with spinous whorls. Cyclura. 



Terrestrial types of flattened form. 



La'manctua. 



Ophryoi'ssa. 

 Tiaris. 



Diporophora. 

 Physignathus. 



