1890.] 



NATURAL SCIENCES OF PHILADELPHIA. 



59 



olecranon process. Dr. Leraoine states that the metacarpals are 

 shorter than the metatarsals. The phalanges spread very slightly 

 and are cleft distally. The brain shows (see '82a) elongate olfac- 

 tory lobes and hemispheres with extremely narrow frontal lobes. 

 The cerebellum is short and extended transversely. 



CREODONTA. 



The following genera belong to three families. Ardocyon 

 to the Ardocyonidae. Hyaenodldis, probably to the Mesonychi- 

 dae. Tricnspiodou cannot at present be classed. Its nearest affini- 

 ties are with Stypolophus or Didyviidis. 



ARCTOCYON, De Blainville. 



A. /n'maevus, De B\a\nv\\\e. A. G^c'r^vn'i'/V, Lem. '78a, p.7 . A Dueilii'LQm 



'78a, p. 8. 



Gen. char.: Dentition if c| p;^ mf. The superior mo- 



1 a r s t r i t u b e r c u 1 a r w i t h a w e 1 1 d e v e 1 o p e d h y p o c o n e. 



The i n f e r i o r molars q u a d r i t u b e r c u 1 a r with the 



p a r a c o n i d usually absent. The ]) r e m o 1 a r s simple. 



The general characters 

 of this genus are too well 

 known to require detailed 

 enumeration here. The 

 type species, A.primaevus, 

 of de la Fere, is the oldest, 

 largest and probably the 

 most primitive ; it has four 

 premolars, the first premo- 

 lar is one rooted. The A. 

 Dueilii (type of Heteroho- 

 rus Cope^), of the Cernay- 

 sian, also has four premo- 



Arctocyon. 



A. Diteilii. b 

 superior molar. 



Fig. 4- 



a, Superior molars referred to lars ; the first premolar is 

 A. Gen'aisli, an unworn second . i j xi, • • 



, ,. A. Ga-i^isii, inferior molar ^WO rootedj the series IS 



series viewed from the crown and external side, i. compact ('78, PI. Ill, fig. 

 d, A. Ger-.aisii, last inferior molar. Abbrev. : y. ^^^ ^j^^ j^^^^^. ■ j^ ^^^_ 

 /r, protocone: /rt, paracone; w^, metacone; ny, ... 

 hypocone; w/, melaconule ; />/, paraconule. ativelyshort,deepandmaS- 



sive ('78a, p. 26). Dr. Lemoine estimates the posterior molar at c80 

 (antero-posterior diameter). The A. Gervaisii (type of Hyodedes, 

 Cope^) is distinguished by three premolars, the elongate and rela- 



^ " Tertiary Vertebrata," p. 259. 



