1892.] ^^* [Cope. 



are three on the suprateniponil ; and in P. douglassii the arrangement is 

 slniihir. Owing to the inferior position of tlie supratemporal, the quad- 

 rate is oblique forwards and downwards. It presents one conch, tiie ex- 

 ternal. Tlie vomers are short, and are separated from each other for the 

 posterior lialf or more of their length by a hiatus, which continues pos- 

 teriorly of about equal width between the palatine and pterygoid pairs. 

 The latter are short, wide and flat, and the palatine foramen is small ; 

 least and oval in P. coronatum ; small and round in P. eornutum ; larger 

 and elongate in P. douglnssti. The ectopterygoid is decurved at its inner 

 extremity. Tlie presphenoid is wanting, and the suture between the 

 sphenoid and the basioccipital is persistent. The supraforaminal pirt of 

 the petrosal is veiy short, and the infraforaminal part is not much pro- 

 duced, and has a wide inferior groove. The epipterygoid originates be- 

 hind the ectopterygoid process, and has the peculiarit}^ among Iguanidae 

 of not reacliing the parietal, but of resting on the anterior border of the 

 petrosal. The occipital condyle shows traces of its tripartite composition. 

 The postoptic is curved and simple and does not reach the frontal bone. 

 The latter is grooved on the middle line below. 



Tlie groove of Meckel's cartilage is open throughout in P. eornutum 

 and P. coronatam and distally only in P. douglassii. The coronoid is not 

 produced horizontally on the external face of the mandible, and the den- 

 tary is not produced beyond its posterior border. This element has a re- 

 flected inferior border in the P. eornutum which is acutely dentate posterior 

 to the middle ; characters absent from P. coronatum and P. douglassii. In 

 P. douglassii the suraugular is not coossified with the articular, while it is 

 so united in the other two species. The angle is short, and is directed 

 downwards and obliquely inwards. 



The basihj'al is wide and is ossified, and the second ceratobranchials 

 are very short and widely separated. The hypohyals are short and carry 

 the ceratohyals on their extremities. No expansions of lateral elements. 



The vertebrae liave no zygosplien articulation, but the prezygapouhy- 

 seal facet is carried upon the side of the neurapophysis at an angle with 

 the usual position. This furnishes the initial step in the production ot a 

 zygosplien. I find five cervical intercentra in P. eornutum and P. eorona- 

 tum, and six in P. douglassii, exclusive of the intercentruni of the atlas, 

 which has no hypapophysis. Ribs extend to the sacrum, and are attached 

 to very short diapopliyses. The two sacral diapophyses are separated by 

 a wide fissure in tlie P. coronatum and P. douglassii, but are closely ap- 

 pressed in P. eornutum. On one side of the skeleton of P. douglassii the 

 last lumbar vertebra carries, abnormally, a third sacral diapophysis 

 which reaches the ilium. Proximal part of caudal vertebra; with long 

 diapophyses. Caudal centra not segmented. Chevron bones intercen- 

 tral, not uniting distally. Neural spines everywhere very low, those of 

 the caudal vertebrae single. 



The suprascapula is exceptionally elongate, and the scapula is of mod- 

 erate length and has a proscapular process. The coracoid has one emar- 



FROC. AJIER. PHILOS. SOC. XXX. 138. 2 A. PRINTED MAY 6, 1892. 



