MORPHOLOGICAL REVISION 



119 



defined than in any of the specimens of Cacops examined. The surface is 

 flattened or with a gentle anteroposterior convexity with sharp rims. It 

 is broadest on the inner side, narrower in the middle, and again somewhat 

 expanded from before back on the outer side. The surface looks backward 

 at an angle of about forty-five degrees from the longitudinal plane of the 

 bone, with a slight obliquity inward. 



"A large part of the left innominate bone is preserved, enough to 

 demonstrate its close resemblance to the corresponding element of Cacops. 

 Nor do the proximal ends of the tibia and ulna differ materially; Hke all the 

 other parts, they are stouter." 



Genus CACOPS Williston. (Plates 17-24.) 

 Cacops aspidephorus Williston. 



Characteristic specimen: A nearly complete skeleton. No. 647 University 

 of Chicago. 



The morphological description of this genus and species is taken from 

 Williston's very full account (72). 



"Skull: Two skulls, nearly complete, and portions of two others have 

 so far been recovered from the matrix. Of these the one in the mounted 

 skeleton was quite complete, but suifered slightly at the front extremity 

 in its collection. The best specimen, however, the one from which the fol- 

 lowing description has been drawn, was a skull quite complete, attached to 

 another skeleton, from which the posterior end of the mandibles only was 

 lost in collecting. This skull is slightly smaller than the mounted one and 

 had suffered very little distortion. It has been freed from every particle 

 of matrix, even that of the brain and nasal cavities. Unfortunately, in none 

 of the specimens has it been possible to determine the sutures, in part because 

 of the complete ossification of the bones; in part, perhaps, because the 

 removal of the thin investing matrix has obliterated whatever indications of 

 them might have been present. The dermal surface is everywhere rugose, 

 with small, irregular pits and ridges. 



"The skull is broad and depressed, broadest opposite the posterior part 

 of the orbits, with a gentle, perhaps somewhat irregular, convexity on the 

 sides. The epiotics project backward strongly, leaving a deep concavity 

 in the middle behind. The nares are large, oval in outline, directed upward, 

 forward, and outward, broadly separated in the middle, and approaching 

 closely the margin of the maxillae. The orbits are large, subcircular in out- 

 line, the opening looking obliquely upward. Near the middle of their front 

 margin the border is angularly thickened, descending in a steep declivity 

 outwardly. In the middle posteriorly, also, there is a similar but more angu- 

 lar thickening, which extends back as a ridge to form the lateral margin 

 of the cranial table, overhanging the otic cavity posteriorly. Almost con- 

 tinuous with the upper orbital margin, there is another elevated ridge 

 running backward and outward to join the lateral border over the middle of 

 the otic cavity. Between these two ridges there is a triangular space of 

 considerable size, more or less depressed in its middle. The least distance 

 between the orbits, near their middle, is but little or no more than one- 

 half the lateral diameter of the orbit. The large parietal opening is located 

 about one-third of the distance between the hind borders of the orbits and 

 the occipital margin in the middle. Just in front of the concave hind border 

 of the table the margin is elevated into a prominent rugose crest or ridge, 



