44 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



Abstract of Broili's analysis of P. isolomus: 



Skull triangular. Orbits large and round. Nares terminal and round. Pari- 

 etal foramen present. Sculpture formed largely of more elongate lines; on the sides 

 the presence of cross lines produced a pretty regular network. Parietal bordered in 

 front by the frontal, postfrontal, and postorbital. The frontal takes small part in 

 the border of the orbits. The pterygoid is tripartite, the anterior portion bears 

 small teeth and the inner edges of the two bones are united anteriorly; posteriorly 

 the edges are separate and between them can be seen the slender parasphenoid 

 rostrum. The posterior portion is extended as a broad plate back to the quadrate. 

 The third (ectopterygoid) portion is truly only a thickening of the posterior border 

 of the anterior portion, but may be spoken of as true process because it is sharply 

 oflFset from the anterior portion behind, though it joins it gradually in front; the 

 teeth on the process in this specimen are destroyed. The jaw teeth are obscured 

 by the fact that the lower jaws are in position, but there are two or three rows of 

 teeth on the maxillary. 



Measurements, j. 



Total length of the skull in the middle line 0-045 



Breadth of the skull, posterior edge 027 



Distance posterior edge of the nares to the anterior edge of orbit Oio 



Distance between nares OO35 



Distance from orbits to posterior edge of skull 016 



Distance between orbits 0085 



Anteroposterior diameter of orbits '0145 



Transverse diameter of orbits OI25 



Revised description: This species resembles C. aguti in most particulars, but 

 the skull is wider and lower in proportion to the length. The difference was at first 

 thought to be due to crushing, especially as the skull o{ aguti is somewhat compressed 

 from side to side, but there is also a notable difference in the proportions of the 

 parietal bone. In skulls of nearly the same length the parietal measures 17.5 mm. 

 in C. angusticeps. No. 4334 Am. Mus. Nat. Hist. Cope Coll., and 24 mm. in C. isolo- 

 mus. No. 4338 Am. Mus. Nat. Hist. Cope Coll. 



Captorhinus aduncus Cope. 

 Pariotichus aduncus Cope, Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 135. 



Type: An imperfect skull and a few fragments of the skeleton. No. 4332 Am. 

 Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: "The species is intermediate in size and characters 

 between the type of the genus P. brachyops and the larger P. aguti, besides presenting 

 a number of peculiarities of its own. The elongate maxillary teeth are graded 

 in size to the smaller; and the sixteenth from behind, the largest, is nearer the an- 

 terior border of the orbit than to the nostril. In front of it are three teeth which are 

 preceded by an interval. There are three and perhaps four incisors on each side, 

 of which the external two are small and the internal two very large, the inner the 

 largest. The mandibular teeth increase regularly in length anteriorly. TTie 

 nostrils are lateral and absolutely terminal. The premaxillary bones are recurved 

 so that the alveolar edge is in vertical line with the posterior border of the nostril. 

 Thus this recurvature exceeds that seen in any other species of the genus, and the 

 symphysis mandibuli is correspondingly posterior. The orbits are larger than in 

 any other species, exceeding the interorbital width considerably, and equaling the 

 length of the muzzle from the orbit to the middle of the nostril. The muzzle is 



