Vol. V] TAYLOR— NEW SUBGENUS OF PHENACOMYS J 35 



upper molar a second outer triangle, which is practically 

 closed off from the inner loop, the antero-external loop on the 

 second lower molar is open, the enamel pattern of the third 

 lower molar is nearly identical, the geographic range is simi- 

 lar, and the proportionate length of the tail is nearly the same. 

 It differs from longicaudus in being darker, in having a faint 

 wash of buffy on the white ventral surface of the body, in its 

 bicolored tail, in the general length and narrowness of its 

 skull, and in its, so far as known, exclusively terrestrial 

 habit. It is practically intermediate between the orophilus- 

 intermediiis series on the one hand and loiizicaudus on the 

 other in width of interorbital constriction, outline and position 

 of postero-inner loop on back upper molar (closer to longi- 

 caudus than to the orophihis-intermedius series in this char- 

 acter), and outline of outer triangle on second lower molar 

 (perhaps closer to the oropJiihis-intermedius series in this 

 character). 



There are several alternatives open in the matter of the dis- 

 position of Phenacomys albipes. It may be left "of uncertain 

 status" ; it may be accorded separate subgeneric rank ; or it 

 may be referred to one or the other of the subgenera 

 Phenacomys and Arborimus. In view of the small amount 

 of material available, there is much to be said in favor of 

 leaving it for the present "of uncertain status." The peculiar 

 slender appearance of its cranium might be regarded as of sep- 

 arate subgeneric value, if it were more striking, or if there 

 were associated with it other characters of importance. Since 

 most of the available evidence seems to point to the dis- 

 position of albipes as a member of the subgenus Arborimus, 

 the species has been assigned thereto by the present writer, 

 but in the absence of more material and information it is 

 emphasized that such reference must necessarily be no more 

 than tentative. 



