DEC 5 1930 



H*--t-- \ 



PAL.EONTOLOGICAL BULLETIN. 



3STO- 14. 



ON SOME NEW EXTINCT MAMMALIA, FROM THE TERTIARY 

 OF THE PLAINS. 



By Edward D. Cope. 

 Aeltjrodon mustelinus, sp. nov. 

 A small single-rooted second molar of the lower jaw. First molar 

 sectorial, with a rather narrow posterior heel, one-third its length, and 

 a small inner tubercle at the base of the second outer cusp. Last pre- 

 molar with a short posterior heel and distinct outer tubercle on the pos- 

 terior side of the cusp. Margin of jaw strongly everted below the mas- 

 seteric fossa. ■ 



M. 



Length of three last molars 018 



" " sectorial " 010 



Width " " " (greatest) 005 



Height posterior cusp, do 005 



This species was about as large as the domestic cat, and less than one- 

 third that of Ac. ferox, Leidy. 



ACERATHERITJM MEGALODTJS, Sp. llOV. 



Represented by a perfect cranium with dentition of both jaws nearly 

 complete, with large portions of fekull and dentition with other bones of 

 other specimens. 



The nasal bones are not coossified, and but little little convex. They 

 are smooth, and long and slender, indicating that this rhinocerus was 

 without a horn. The inion is anterior to the line of the occipital con- 

 dyles and is considerably elevated and bilobed. The temporal fossae ap- 

 proach each other, being separated by a narrow rib only. The ramus 

 mandibuli is rather slender, and projects well in front of the line of the 

 nasals. The dentition is I. |; C. %; P. M. - ( ^'M. f. The usual anterior 

 premolars are wanting in the lower jaw, and in the upper jaw in one 

 specimen, and on the right side of the other ; hence I suspect § to be the 

 normal dentition of the species, are £ in Rhinoceros and Aceratherium, the 

 present animal may be placed in another genus under the name of Aphe- 

 lops. The middle incisors were cardicous. The outers are very large 

 and cylindric at base ; the attrition of their inner faces would indicate an 

 opposing pair, but these I did not find, and the premaxillary sutures of 

 the maxillary are exceedingly slender. 



The first lower premolars are not very narrow. The transverse crests 

 of the superior molars widen inwardly, but do not come into contact 

 with each. On the posterior margin of the posterior is a deep notch 

 which almost divides it across. There are no other lobes. The last 

 molar is narrowed. These teeth are notable for their. very large size, as 



