104 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



wall. These bones unite at their outer end with the upper part of the so-called 

 epiotic; the lower, thin and somewhat concave border is free. The epiotics are 

 broader and longer than this postparietal, with nearly parallel sides, the lower 

 margin thinned and free and concave in outline, the upper uniting by suture with 

 the squamosal at the angle of the skull. The inner end, which is truncate, unites 

 above with the 'postparietal'; below it presents an oblique articular facet for union 

 with the extremity of the paroccipital. The outer extremity is rounded below, and 

 extends to the angle of the skull, articulating apparently with the posterior end of 

 the jugal. On its inner surface near the roof it articulates for a large part of its 

 extent with the hind border of the quadrate. Further observations on the homol- 

 ogies of this remarkable bone will be given later. 



"The more complete of the two larger skulls has the palatal and basicranial 

 regions in excellent preservation, and but little distorted. Just back of the trans- 

 verse bones a recent fracture through the narrowest parts of the free pterygoids has 

 permitted the removal of the posterior portion and its complete separation from the 

 incrusting matrix, both above and below, enabling one for almost the first time to 

 obtain a clear conception of the cranial bones and their relations to each other. 

 Very remarkable is the fact that all this portion has no sutural connection with the 

 cranial walls, the suture between the quadrate and the epiotic being the only one, 

 indirectly connecting the vertical elements with the superior membrane bones. 

 This will readily account for the fact so often observed, of the loss of the basioc- 

 cipital and basisphenoid from the remainder of the skull, a loss which, erroneously 

 interpreted, induced Cope to give the name Cotylosauria to the whole group. Above, 

 in the middle, the 'postparietals' merely touch the supraoccipital, while the epiptery- 

 goids further in advance touch the parietals in a mere rounded point. 



"The quadrate bone of the left side in this specimen lacks its articular head, 

 which had been, unfortunately, broken off with a part of the articular and lost before 

 the discovery of the specimen. The remainder of the quadrate, however, is quite 

 in position, overlapping the pterygoids, and is complete. On the right side the 

 quadrate, nearly complete, has been entirely separated from its articular relations. 

 The vomers, anterior part of the pterygoids, the palatines and the transverse bones 

 are all in their normal positions. The nares, situated far in front, probably directly 

 below the external orifices, are concealed by the mandibles, which are closed upon the 

 maxillae; nor is the suture distinguishing the vomers from the posterior elements 

 distinguishable. The narrow pterygo-palatine shelf on each side shows, on the upper 

 side at least, a suture between the palatines and pterygoids for a portion of the dis- 

 tance, though I can make out no suture separating the transverse bones, though such 

 doubtless existed. The transverse bones are stout, forming a strong declivity from 

 the plane of the palatines, and they abut massively against the mandibles at least 

 as far as their middle. In the middle, between the pterygoids, opposite and in front 

 of the transverse bones, there is a large ovate interpterygoidal space, in front of which 

 the two pterygoids approach each other closely, though not touching. Possibly 

 in the living skull they actually met in the middle. In front of the basisphenoid the 

 pterygoids curve inward so that they meet in the middle behind, leaving no space 

 for a presphenoid or parasphenoid, which is certainly wanting in this, specimen at 

 least, though distinctly present in a smaller skull, and recognized by Broili in this 

 species. The pterygoids unite firmly with the basisphenoid by this inner sphenoid 

 process. Along the margin of the interpterygoidal opening, for nearly its whole 

 extent, there is a row, possibly double in front, of small tubercular teeth; a patch of 

 similar teeth is also present in front of the transverse declivity of the palatines, and 

 yet another patch on the summit of each transverse bone. 



