862 THE JOHN DAT FAUNA. 



bulla is angulate along the inferior middle line, and has a narrower fonn 

 than that of any of the other species of the genus. The bottle-neck processes 

 send out prolongations, which meet on the middle line below. The mastoid is 

 convex posteriorly, but carries a lateral occipital angle above. 



The molars of the superior series are. fissured on the external side for a 

 distance, and the anterior is like the others in both jaws. The superior in- 

 cisors are slightly convex anteriorly, and are pei'fectly smooth, except a 

 delicate groove close to the inner border, a character found in most of the 

 other species. 



The masseteric ridge of the mandible extends as far forward as the 



line of the front of the first inferior molar, and is well defined posteriorly to 



near the angle. 



Measurements. 



M. 



Lengt h of skull from front of premaxillary bone to posterior face of mastoid 038 



Length from front of premaxillary to base of Pm. iv — 018 



Length of molar series on base 0066 



Width of otic bulla at middle 0040 



Length of bulla and mastoid 0110 



Width of muzzle at middle 0080 



Width of interorbital space 00.i5 



Depth of mandible at M. i 0060 



John Day River, Oregon. 



Entoptychus cavifrons Cope. 



Paleontological Bulletin No. 30, p. 2. Proceedings American Philosophical Society, 1878 (1879), p. 64. 



Plate LXIV; fig. 4. 



I refer portions of six crania to individuals of this species, and seven 

 othei's probably belong to it. It differs from the JE. minor in its superior 

 size, and in the presence of superciliary ridges. These ridges are rarely as 

 thick and prominent as in the Pleurolicus sulcifrons, and do not appi'oacli the 

 development seen in the Entoptychus crassiramis. 



The postorbital part of the skull is subquadi'ate in outline and depressed 

 in form. The interorbital region is narrowed, but the superciliary margins 

 do not meet nor converge to form a sagittal crest. They are thickened, 

 forming two subparallel ridges which are separated by a shallow concavity 

 of the frontal bone. The nasal bones are very narrow, and their posterior 

 apices just attain the line of the supero-anterior angle of the orbit. The 



