384 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



vex and horizontal, bat contract directly into the temporal fossae. The 

 nasal bones are very short and small, ceasing above the third superior 

 molar. The anteorbital region is concave, and there are three infra- 

 orbital foramina, one within the nasal cavity. The superior edge of the 

 maxillary is broadly incurved. There are two lachrymal foramina, both 

 within the orbit. The palatine and pterygoid regions are wider than in 

 A. fossiger, and the pterygoid processes of the alisphenoid originate 

 farther back. The crowns of the molars are short, with posterior notch 

 not inclosed, and resemble those of A. megalodus. 



• Measurements. 



M. 



Length of skull to first premolar along base 0.550 



Length of true molar series 0.160 



antero-posterior 0.062 



Diameter of second true molar ^ , n neo 



I transverse O.Ub^ 



Width of palate between bases of third true molars 0.110 



Interorbital width 0.230 



Length of freepart of nasal bones 0.140 



Elevation of occiput from base 0.220 



This rhinoceros is quite unlike anything yet discovered. I possess 

 a fine cranium, which was found in the Loup Fork beds of Kansas by 

 my assistant, R. S. Hill. 



Mylagaulus sesquipedalis, gen. et sp. nov. 



Char. gen. — Order Bodentia. Eepresented by a molar tooth, which is 

 the first or last of the series. It is rootless, and is oval in section, the 

 long diameter being probably transverse to the long axis of the cranium, 

 and shortening toward the apex of the crown. Shaft curved in the di- 

 rection of its short diameter. The tooth is inclosed in an uninterrupted 

 sheath of enamel, without inflections. Within this are several enamel 

 tubes, which form oval and crescentic figures in section on attrition. 

 The long diameters of these are parallel with those of the crown. 



The peculiar molar tooth which indicates the genus above described 

 is not comparable to that of any recent or extinct type now known from 

 this continent. The entire inclosure of the subordinate enamel areas 

 within the investing cylinder resembles most the arrangement seen in 

 the inferior molars of some species of Dasyprocta when much worn, and 

 it is quite probable that the genus Mylagaulus belongs to the same 

 family. It differs from the genera which are known in the transverse 

 relation of the long diameter of this tooth to that of the skull, as well 

 as in the resulting narrow forms of the inclosed enamel areas. It is 

 possible that in an earlier stage of wear some of these areas may have 

 opened on the internal or external faces of the tooth, but this is, of 

 course, uncertain, and is less probable than if the fore-and-aft diameter 

 of the crown were greater. 



CTiar. specif. — Grinding surface a regular oval. Enamel areas two 

 longer and four shorter. Of the former, one is an open crescent, extend- 

 ing from near one extremity of the grinding face to near its middle j the 



