﻿Dec, 1895.] 



KEY TO SPECIES NORTH OF MEXICO. 



59 



KEY TO SPECIES OF SOKEX PROPER. 



A. Species Uvinfj north of Mexico. 



Size very large (total lengtli abont 150 mm. ; hind foot, 17 mm.) pacificus 



Size medium or small (total length never more than 135 mm.; hind foot, 

 15.5 mm. or less). 

 Third nnicnspid larger than fourth. 



Size rather large (head and body about 70 mm.). 



Coloration distinctly tricolor (sides different from back). 



Hind foot about 14 mm.; tail about 40 mm.; skull, 20 mm ricliardsoiii 



Hind foot about 13 mm. ; tail about 35 mm. ; skull, 16 mm prihilofensis 



Coloration bicolor (sides same color as back). 



Color plumbeous or sepia brown; pelage normal fnmens 



Color ahnost sootj^ black; pelage exceedingly long spihagnicola 



Size rather small (head and body about 60 mm.). 



Skull short and broad; unicuspids ou same plane with molars merriami 



Skall long and narrow; unicuspid series strongly deflected, forming 

 angle with molar series. 



Tail about 40 mm. or less personatns 



Tail 45 nun. or more u-. streatori 



Third nnicuspul smaller than fourth. 

 Hind foot about 15 mm. 



Anterior unicuspids much swollen hairdi 



Anterior unicuspids not nuich swollen. 



Color dark plumbeous or sooty montereyensis 



Color dull chestnut brown, varying to sepia brown. 



Tail very long (about 60 mm.) longicauda . 



Tail medium (about 50 mm.) alascensis 



Hind foot about 14 mm. or less. 



Hind foot about 14 mm. (color dark plumbeous or sooty) troichridgii 



Hind foot about 13 mm. or less. 



Sides pale ; rump with a dark patch ; molariform teeth broadly and 



deeply excavated posteriorly ornatns /■' 



Coloration normal; excavation of molariform teeth moderate. 

 Hind foot about 13 mm. 



Tail less than 45 mm dohsoni 



Tail more than 45 mm ohscurus • . 



Hind foot decidedly less than 13 mm. 

 Brain case low and flat. 



Brain case broadly rounded ccdifornicns 



Brain case narrow. 



Hind foot more than 12 mm tenellns 



Hind foot about 10 mm - nanus 



Brain case nonnal. 

 Total length less than 100 mm. 



Coloration tricolor; sules much paler than back nevadensis 



Coloration normal ; sides not paler than back. 



Hind foot less than 11mm longirostris 



Hind foot 12 mm or more fisheri 



Total length more than 100 mm. 



Tail less than 40 mm. ; color dusky or sooty amcenus 



Tail more than 40 mm. 



Color pale sepia brown monticola 



Color dark. 



Back and sides dark brown, varying to almost russet., vagrans 

 Back almost dusky; sides sepia brown vancouverensis 



