1?92.] 203 [Cope. 



pterygoid processes. Ectopterygoids depressed internally, Epipterygoid 

 originating behind ectopterygoid process, and reaching parietal without 

 contact with petrosal. Prespbenoid rudimental ; sphenoid and basioccip- 

 ital confluent. Occipital condyle plain, with exoccipilal elements not 

 distinct. The fenestra ovale and foramen of viii nerve sunk in deep 

 fossae. 



In the mandible the terminal part of Meckel's cartilage is exposed. The 

 coronoid has no extension on the external face, and extends a short distance 

 forwards on the inner face. The splenial is rather elongate, and extends 

 anterior to the splenial foramen. The dentary extends to the line of the 

 posterior border of the coronoid above, and of its anterior border below. 

 In old individuals the surangular and articular are fused. The angle is 

 pinched, and sends inwards a horizontal process similar to its posterior 

 process. 



In the hyoid apparatus the ceratobrancliials of the second pair are 

 closely appressed, thus supporting a median gular angle. The hypohyals 

 are moderately long, and they join by their extremities the ceratohyals, 

 which have no expansions, and are of only moderate length. 



The scapula has a well-developed proscapula, and there are two deep 

 emarginations of the coracoid. The sternum has a narrow longitudinal 

 median fontanelle in tlie G. collaris, andno fontanelle in C. wisUcenii (one 

 specimen of each examined). There are four ribs articulating directly 

 with the sternum on each side, and two via each xiphoid rod. Tiie latter 

 are not closely appressed as in some, nor so widely separated as in other 

 Iguanidfe. 



Vertebrae without zygnsphenal articulation, but the prezygapophyseal 

 faces concave. Cervical vertebrae eight, the anterior five vertebrae with six 

 free intercentra in C. wisUcenii, and four vertebrae with five intercentra in 

 C collaris, anterior three vertebrae without ribs in both species. The 

 neural spines are very low on the dorsal vertebrae, and are a little more 

 elevated on the caudals. The latter have a projecting keel towards the 

 anterior part in the C wislieenii (wanting in C. collaris), which represents 

 the anterior neural spine of Dipaosaurus dorsalis. The centra in Crotaphy- 

 tus are not segmented. Diapophyses are present, but are nowhere long. 

 Short ribs extend to the sacrum. 



The teeth are tricuspid, but in the two species examined the lateral 

 cusps are rudimental. Anterolateral and incisor teeth simple, subequal. 

 The pubes unite at an exceedingly open angle, and the pectineal pro- 

 cess is submedian. Tuber ischii prominent ; a small angle or crista ilii. 

 Acetabulum entire posterioi-ly. 



The principal characters in which the skeleton of the Crotaphytus differs 

 from Dipsosaurus are the following : Nasal bones shortened in front ; no 

 postfrontals ; pineal foramen connected with coronal suture ; Meckelian 

 canal partly open ; two notches of coracoid ; xiphoid rods not appressed ; 

 no zygosphen ; caudal centra not divided ; acetabulum not deeply 

 notched. 



