MYOMOEPHA. 861 



E. cavifrons, so that its validity may be thought to be as yet not entirely be- 

 yond question. 



In this species, the interorbital region is concave, but there is no ridge- 

 like thickening of the supraorbital border. It presents, on the contrary, a 

 subacute sujjerior edge, flush with the inferior part of the same border. 

 These edges leave the orbital border posteriorly, and converge in straight 

 lines to an acute angle, forming two temporal ridges. The nasal bones 

 do not extend as far posteriorly as the premaxillaries, which reach to the 

 inner line of the anterior border of the orbit. The anterior molar tooth is 

 like the others, and has no anterior basal extension. 



The size is about equal to that of E. planifrons. 



Measurements. 



If. 



Interorbital ^yidtll 0064 



Anteroposterior length of orbit 0100 



Depth of skull to alveolar edge 0140 



Length of series of suiierior molars • 0070 



Width between bases of Pm. iv 0030 



The skull above referred to presents the temporal ridges of the typical 

 specimens. It has also lateral occipital angle of the mastoid, as in E. plani- 

 frons, and a meatal tube nearly as long as in that species, differing in both 

 points from the E. cavifrons. But it has a ridge-like thickening of the 

 supraorbital border, as in that species, and the interorbital space has the same 

 relative width. 



Its size is that of E. cavifrons. 



Entoptychus minor Cope. 



Bulletin U. S. Geol. Surv. Terrs., IV, 379. 

 Plate LXIV ; iig. 3. 



This was an abundant species. Eight more or less complete crania 

 are in my collection, and many fragments present the characteristic meas- 

 urements. It is the smallest species, and is characterized also by the per- 

 fectl)^ flat interorbital region and the absence of temporal ridges. 



The muzzle of the skull is shorter than in E. planifrons, as may be seen 

 by the measurements, and it is also narrower above, as compared with the 

 interorbital width. The preorbital fossa is not well defined in front. The otie 



