1915.] 



GENUS SCAPANUS? 



57 



slight cusplike process posteriorly; fourth premolar much larger, 

 more cuspidate. Lower molars M -shaped in transverse section, the 

 antero-internal cusp bilobed; first molar with a postero-internal 

 basal accessory cusp ; second molar with a postero- and an antero- 

 internal basal accessory cusp; third molar with an antero-internal 

 basal accessory cusp; first and second molars subequal, the third 

 much smaller. Dentition: i. f ; c. \; pm. f ;^ m. f ; total 44. 



Key to Species and Subspecies of Scapanus. 



[Based upon specimens of adult animals in fresh pelage.] 



a^. Unicuspid teeth evenly spaced and not crowded; rostrum relatively long and nar- 

 row; color dark, almost black (except in Scapanus orarius schefferi). 

 h^. Total length more than 200 mm.; greatest length of skull more than 40 mm.; 



sublachiymal-maxillary ridge distinct Scapanus townsendii (p. 58). 



Total length less than 200 mm. ; greatest length of skull less than 40 mm. ; sub- 

 lachrymal-maxillary ridge not much developed, 

 c^. Color darker; rostrum narrow; interorbital breadth of skull 8.2 mm. or less, 



Scapanus orarius orarius (p. 61). 

 c^. Color paler; rostrum relatively broad; interorbital breadth of skull 8.2 mm. 



or more Scapanus orarius schefferi (p. 63). 



a^. Unicuspid teeth usually crowded and not evenly spaced; rostrum relatively short 

 and broad; color usually brown or gray, seldom almost black. 

 6^ Total length usually less than 165 mm. ; greatest length of skull 33.5 mm. or less. 

 c\ Greatest length of skull less than 31 mm. ; premolars f , 



Scapanus anihonyi (p. 75). 

 c^. Greatest length of skull 31 mm. or more; premolars |. 

 d}. Interorbital constriction more than 7.6 mm.; breadth of skull across mas- 

 toids more than 16.2 mm Scapanus latimanus grinnelli (p. 69). 



cP. Interorbital constriction 7.6 mm. or less; breadth of skull across mastoids 

 16.2 mm. or less. 



e^. Inferior mandibular notch deep; geographic range south of latitude 



37° N Scapanus latimanus occultus (p. 68). 



e^. Inferior mandibular notch shallow; geographic range north of latitude 



37° N .Scapanus latimanus rainuscfulus (p. 72). 



Total length usually more than 165 mm.; greatest length of skull more than 

 33.5 mm. 



Geographic range, California west of Sacramento and San Joaquin Valleys, 



including also Klamath Canyon Scapanus latimanus latimanus (p. 64). 



c^. Geographic range, Oregon and California east of Sacramento and San Joaquin 

 Valleys, except Klamath Canyon. 

 d^. Color dark; interorbital constriction less than 7.6 mm., 



Scapanus latimanus sericatus (ip . 71). 

 c?2. Color pale; interorbital constriction more than 7.6 mm. 

 e^. Greatest length of skull less than 36 mm., 



Scapanus latimanus dilatus (p. 72). 

 e^. Greatest length of skull more than 36 mm. , 



Scapanus latimanus alpinus (p. 75). 



1 Pm. I in the type and only specimen of Scapanus anthonyi. 



