IGrAXII)J5. 



to a slight degree by one genus only (Uraniscodon) ; in all others 

 the teeth are subequal in size, and if, as is usually the case, the 

 lateral ones differ from the front ones, the change is gradual. In 

 all genera save Amhhj rlujnchus, Conolophus, and Phymaturus, the 

 anterior teeth are conical ; the lateral ones are also sometimes simply 

 conical or with obtuse crowns, but more frequently compressed and 

 tricuspid ; in Ljuana and Metopoceros the crowns are finely denticu- 

 lated on the edge. In the above-named highly remarkable genera 

 Aiiihhirliipiclms, Conoloplms, and Phijmaturus, all the teeth are 

 deeply trilobate, or flower-de-luce shaped. The shafts of the teeth 

 are constantly long and cylindrical, and hollowed out at the base. 

 Pterygoid teeth are present in many species; I have not employed 

 this character for the distinction of genera unless accompanied by 

 others. ChamreleoJis is one of the few Lizards in which teeth are 

 inserted on the palatine bones. 



The skull does not differ in any important point from that of the 

 Agamkhv. However, dermal cranial ossifications, as, for instance, 

 the horn-like tubercles of Phrynosoma^ may be jH'esent. A sujjra- 

 orbital arch, such as has been noticed in the Agamoid genus Lyrio- 

 ceplialus, occurs in Corythop>lianes and Phrynosoma. The clavicle is 

 slender proximally, except in the genera Basiliscus and Lmnanctus. 

 In describing the Iguania as having the " clavicle with simple 

 proximal ends," Cope * remarks in a footnote that " the transverse 

 limb of the mesosternum [sternum, nobis] extending to the angle of 

 the clavicle, gives an appearance in some of the Basiliscina; of a 

 proximal foramen." I had hitherto held this opinion to be correct, 

 but now find, on careful examination of the pectoral arch of the types 

 alluded to, that the clavicle is really loop-shaped, and that those two 

 genera constitute an exception in the family Igaanida', which is cha- 

 racterized by a non-dilated clavicle. The interclavicle is T- or anchor- 

 shaped, exceptinP/in/HosoHirt, in which the longitudinal limb is absent. 

 The sternum is frequently perforated by a fontanelle. A more or 

 less complete system of ossified or tendinous abdominal ribs is deve- 

 loped in many genera, in some (AnoJLs, Polychrus, Liosaurns, &c.) 

 to the same extent as in the Gechonidn'. 



The tongue is thick and villose, entirely fixed to the floor of the 

 mouth, or slightly free anteriorly, and not or but very feebly nicked. 

 The pupil of the eye is round, and the eyelids well developed. The 

 tympanum is distinct, except in Holhroolia. 



Femoral pores exist in all North- American genera, and are absent 

 in the great majority of the South- American. In some of the 

 latter the males have a series of pores on the anterior border of the 

 vent. 



The scaling of the head and body varies extremely, and gular 

 appendages, crests, and other ornaments are not uufrequent. The 

 upper head-scales are usually small, but in some genera assume a 



Proc. Ac. Philad. 18G4, p. 227. 



