﻿72 



NORTH AMERICAN FAUNA. 



[No. 10. 



General remarl^s, — Sorex nevadensis is an easily recognized species, its 

 dark back, finely mixed with hoary, and indistinctly tricolor coloration 

 which snggests -8'. ricJiardsoni, serving to distingnish it from its nearest 

 allies. It is the only Shrew thus far discovered in the interior of the 

 Great Basin. 



SOREX OBSCURUS Merriam. 

 (PL VIIl. figs. 1. la.) 



Sorex vagrans similis ^lerriam, >7. Am, Fauua. Xo. 5, pp. 34-35, PL IV. fig. 3, August. 

 1891. i^Xame preoccupied hy Sorex similis HenseL 1855,' and here changed to 

 obscurus.) 



Type locality.-— TimhQY Creek. Salmon Eiver Mountains, Idaho (alti- 

 tude, 8,200 feet). 



Geographic disirihution. — British. Columbia and mountains of western 

 Washington, Idaho, Montana, Wyoming, Utah, and Colorado; south 

 along the High Sierra Nevada in California to Mount Whitney. 

 Eestricted to Boreal zone. 



General characters. — Size rather small; tail about equal to body with- 

 out head; ears inconspicuous; third unicuspid much smaller than 

 fourth. Similar to Sorer dohsoni. but with smaller ears, broader palate, 

 and broader unicuspidate teeth. Compared with S. vagrans, it is 

 slightly larger, with longer tail and larger molariform teeth. 



Color. — Upper x^arts uniform dull sepia brown, nnder x)arts ashy; 

 tail bicolor: upper side concolor with back or slightly darker, under 

 side whitish. In winter pelage the upper parts are ash gray and the 

 under parts nearly white. 



Cranial and dental cliaracters. — Skull similar to that of 8, dobsoni, but 

 l^alate broader; molariform teeth larger; unicuspidate teeth broader, 

 particularly the first and second; third unicuspid decidedly smaller 

 than fourth. Compared with 8. vagrans, the skull is slightly longer 

 (averaging 18 mm. instead of 17 mm.), with larger and heavier molari- 

 form teeth (particularly the large upper premolar) and broader first 

 and second imicuspids. The actual differences in the size of the molari- 

 form teeth are shown in the following table: 



2Iean ineasurements of upper molariform ieetli of Sorex olscuriis, dotsoni, and vagrans. 



[Measareraents in mm.] 



Species. 



Locality. 



Series. rt 



pm. 



ml. 



m2. 



Sorex obscurus 



Salmon River Mountains. Idaho 



Saw Tooth Monutains. Idaho 



Aberdeen, Wash 



400 

 372 

 345 



145 

 137 

 125 



140 

 128 

 120 



12C 

 115 

 105 



a From antero-external angle of pm to postero-external angle of m^. 



1 Hensel, Zeitschr. der Deutsch. Geolog. Gesellsch., YII, 1855, 459. From bone 

 deposits of Cagliari, Sardinia. 



