COPE ON NEW EXTINCT VERTEBEATA. 383 



closed below by contact of the mastoid and squamosal bones, which do 

 not co-ossify. The temporal fossae are only separated above by a nar- 

 row, low, median ridge, which is obsolete in some specimens. The 

 top of the skull is horizontal in profile, as is the zygoma. The pre- 

 orbital region is convex, and the supraorbital border is horizontal and 

 convex. Infraorbital foramen above the third premolar, and the other 

 above and behind the former. In the best preserved cranium, the 

 molars of the right side are preserved. These are markable for the 

 great depth of their sinuses, the posterior notch being closed very early, 

 and forming a deep, isolated pit. The transverse valley is almost closed 

 by the protuberances of its walls, and is strongly curved backward at 

 its extremity. In the same specimen, the inner extremity of the anterior 

 crest of the true molars is pinched into a peninsula by two opposite ver- 

 tical grooves. No cingulum on the inner base of the true molars. The 

 teeth are of relatively large size. 



In a fourth specimen, the posterior part of the mandibular ramus is 

 preserved. This has the flat, anterior base of the coronoid process, and 

 compressed ramus of the A. megalodus, as distinguished from A. crassus 

 and A. jemezamis, but the form is quite different from that in the 

 first-named species. The last molar is considerably in advance of the 

 base of the coronoid, and the latter, instead of rising vertically, slopes 

 away posteriorly toward the condyle. The latter is unusually robust. 

 The masseteric fossa is deeper than in the A. megalodus, as is also the 

 pterygoid fossa. 



Measurements. 



M. 



Lengtli of skull along base to front of third premolar 0.550 



Width of occiput above middle 0.200 



Elevation of occiput , 0.230 



Depth of zygoma at orbit 0.075 



LeugthofPm. 2-3 + M. 1-2-3 0.280 



Length of true molar series , 0.190 



Length of second true molar 0.072 



Width of second true molar 0.080 



Width of third true molar 0.075 



Length of third true molar 0.062 



Width of palate between bases of third true molars 0.070 



In A. megalodus, the occiput is narrowed upward instead of widened, 

 the tooth-crowns are short, and the nasal bones are long, extending 

 anterior to the entire dental series. It is a smaller species; the type- 

 specimens are adult, while in the skull of A. fossiger, above described, 

 the last molar is not fully protruded. 



Aphelops malacorhinus, sp. nov. 



This large species presents many differences from the A. fossiger and 

 A. megalodus. The parietal region rises obliquely from the front to an 

 elevated occiput. The zygoma slopes obliquely upward and backward. 

 The interorbital region is wide, but the superciliary borders are not con- 



