Vol. V] TAYLOR- -NEW SUBGENUS OF PHENACOMYS \\^ 



C ARBORIMUS, A NEW SUBGENUS OF 

 PHENACOMYS 



I Geographic distribution of type species and 



SUBGENUS. 



Phenacoinys loiigicaudiis True, the type species of the new 

 subgenus, is found in southwestern Washington and north- 

 western Cahfornia. Phcnaconiys albipes, tentatively referred 

 to Arhor'unus, occurs in the same general locahty. (See map, 

 fig. 4, p. 137.) 



II Essential characters of Arborimiis. 



Palate tending to be different posteriorly from that in the 

 subgenus Plienaconiys. 



M^ with second outer triangle tending to be closed off from 

 posterior loop ; posterior loop tending to be more rounded, 

 and less emphatically drawn out antero-posteriorly than in 

 Phenacomys. 



Triangles and loops of Mi tending to open into one another, 

 except in albipes. 



Antero-external loop of M2 never closed off, tending to be 

 smaller than in most examples of Phenacomys. 



Outer triangle on M2 tending to be smaller and to open into 

 opposing triangles, except in albipes. 



Ms ordinarily simpler than in Phenacomys, practically three 

 transverse crescents without external triangle. 



Interorbital constriction tending to be narrower than in 

 Phenacomys. 



Tail proportionally decidedly longer than in Phenacomys. 



Color a brilliant reddish, except in albipes. 



Habit arboreal, except in albipes, nesting and apparently 

 living entirely in trees. 



Distribution, humid coast belt of southwestern Oregon and 

 northwestern California, a section in which no specimen of 

 the subgenus Phenacomys has ever been found. 



Ill Description of Phenacomys longicaudus True 



1 cranial characters 



(1) Skull in general 

 Similar in general characters to that of Phenacomys. Crania 

 of Phenacomys (Arborimiis) longicaudus have broader brain- 



