1883.] ^^« [Cope. 



Measurements. M. 



Length of last four inferior molars 0315 



' ' true molars 0230 



/ anteroposterior 0085 



Diameters of M.i.^^^^^^3^,^^.g^ 0055 



Length of P-m. iv. on base 0090 



Depth of ramus at M.i 0200 



Thickness " " 0085 



This Tn'isodon is not only materially smaller than the T. heilprimanus, 

 but differs in the characters of the heel of the inferior molars. In that 

 species the internal border is tubercular ; in this one it is entire. The 

 T. conidens and T. quivirensis differ in the arrangement of the anterior 

 cusps. 



Dedicated to my friend, Henry Carvill Lewis, professor of mineralogy 

 and geology in the Academy of Natural Sciences, Philadelphia. 



MlOCL^NUS FEROX, Sp. UOV. 



This new species is represented by three specimens. One of these in- 

 cludes various separate teeth and a considerable portion of the skeleton ; a 

 second includes loose teeth and a smaller number of bones of the skeleton ; 

 and the third consists of a part of a mandibular ramus, which contains the 

 three true molars. These indicate the largest species of the genus yet 

 known, the first individual above mentioned being about the size of a wolf. 



The bones of the Miocloenus ferox enable me to refer the genus approxi- 

 mately to its proper position in the system. Although we do not possess 

 the corresponding parts of the Mioclcenus turgidus, the type of the genus, 

 it is probable, if not certain, that they agree in generic characters. The 

 agreement in dentition extends to all the principal technical points, though 

 the specific differences are marked. 



The skeleton is that of a creodont. The unequal phlanges are compressed 

 claw^s, and the metapodial bones have protuberant condyles. The astrag- 

 alus has a simple head with convex surface, and the trochlea is a shallow 

 open groove. 



The tubercular dentition refers this genus to the Arctocyonidce* With 

 this family it is accordingly placed provisionally. It differs from the known 

 fossil genera in the single tubercle of the internal part of the crown of the 

 superior molars. 



The species M. hrachystomus and M. etsagicus of the Wasatch epoch must 

 now be removed from this genus. I have shown that the former is an Artio- 

 dactyle. Now in technical points, the dentition of those species is identi- 

 cal with that of Pantolestes Cope, as well as with Mioelmnvs. Although the 

 skeleton of the iy]}Q of Pantolestes, P. Zon-^rzcaMdMS of the Bridger Beds, is yet 

 unknown, it is safe to suppose that it does not differ from that of the M. 

 hrachystomus. I therefore refer the two species first mentioned to Panto- 

 lestes, and place that genus in the Artiodactyle sub-order. 



* For the dentition of this family see Lemoine, Annates, So. Nat., 1S78, July. 



PROC. AMER. PHILOS. SOC. XX. 113. 3q. PRINTED FEBRUARY 14, 1883. 



