FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 233 



able assignment. Our present greatly expanded knowledge of Middle 

 Pal eocene hyopsodontids, however, throws emphasis on certain charac- 

 ters that now appear to be more important phyletically than those 

 previously apparent. The premolar inflation is unlike Oxyacodon 

 both in kind and degree and points toward Mioclaenus, s. s., and not 

 Ellipsodon. In the lower molars the position, shape, and connections 

 of the paraconid are very much unlike Oxyacodon and point toward 

 Mioclaenus and Ellipsodon rather than toward Litomylus and Hap- 

 laletes (described since Matthew's death) as does Oxyacodon. The 

 entoconids are, indeed, distinct, an Oxyacodon-like character, but they 

 are definitely fusing with the hypoconulid and do not suggest continued 

 independence as in the group to which Oxyacodon belongs. (No Middle 

 Paleocene genus known to Matthew belonged to this group, although 

 it is now richly represented, and so he could not evaluate the impor- 

 tance of this character.) The upper teeth are not known in true 

 Oxyacodon, but the characters of the lower teeth sharply distinguish 

 Choeroclaenus from that genus. 



Genus ELLIPSODON Scott, 1892 



This genus is revised in Matthew's memoir. It is unusually varied 

 in structure, and the species here referred to it increases this variety. 

 Ellipsodon aquilonius, of this fauna, closely resembles E. acolytus. The 

 latter is fairly close to E. lemuroides, which in turn approaches E. 

 inaequidens. There is no logical or convenient separation, probably 

 of more than specific rank, in this series of four species, yet E. aquilonius 

 is markedly unlike E. inaequidens, which is the type of the genus. 

 Whether any generic or subgeneric separation is proper, must depend 

 on future discovery. At present it seems that the genus may be too 

 broadly drawn, but this is not demonstrated inequivocably, and it 

 probably is a natural genus in the sense that the species referred to it 

 are related to each other. 



The type species, E. inaequidens, is poorly known. The type speci- 

 men is a palate with P^-M^ of one side or both, all the teeth deeply 

 worn, and the palate encased in hard concretion. Another palate is 

 less worn, but even more obscured by concretion, and a third shows 

 M^~^ fairly well preserved. Lov/er jaw fragments reveal P4-M3. All 

 the few surely referable specimens were collected by Baldwin for Cope 

 in 1882 to 1885, and the great collections made subsequently contain 

 only one specimen possibly referable to the species, and this one is 

 highly dubious. As far as their localities are recorded, Baldwin's 

 specimens all came from Gallegos Canyon, and it is possible that they 

 are from some local pocket worked out by him or not well exposed 

 when later collectors visited the area. The unusual circumstance 

 that the type is the poorest known species of the genus and has not 

 turned up in new collections for over 50 years makes the status of the 



