70 



NORTH AMERICAN FAUNA. 



[No. 38. 



Type specimen. — No. 17785, Mus. Vert. ZooL, Univ. California; <^ 

 adult, skin and skull; collected May 8, 1912, by H. A. Carr. 



Geographic range. — Known only from type locality. 



General cJiaracters. — Size small; very slightly larger than average 

 specimens of S. I. occultus or ;S^. Z. minusculus; smaller than S. I. 

 sericatus; color darkest of the latimanus group ; skull short and high, 

 broad interorbitally and through mastoids; rostrum short and wide. 



Color. — Type, in worn and somewhat faded winter pelage: Upper- 

 parts between fuscous and fuscous-black; underparts more grayish, 

 stained on the throat and chest with Dresden brown. Topotype, 

 in fresh summer pelage: Upperparts fuscous-black; underparts dark 

 mouse gray. 



Slcull. — Short and high, not much depressed postorbi tally, broad 

 interorbitally and through the mastoids; posterior base of zygoma 

 with a small inconspicuous process on outer lateral m^argin; rostrum 

 short and wide; angle of mandible short and heavy. The skull of 

 grinnelli is about the size of large skulls of S. I. occultus, but differs 

 from them, in its higher braincase, its shorter and much broader 

 rostrum, and in being much wider interorbitally and through the 

 mastoids. It is much smaller and relatively shorter and wider than 

 the skull of either S. I. latimanus or S. I. sericatus. 



Measurements. — Type (adult male): Total length, 156; tail verte- 

 brse, 31; hind foot, 21. Topotype (adult female) : Total length, 158; 

 tail vertebrse, 36; hind foot, 20.5 Slcull: Type (adult male) : Greatest 

 length, 33; palatilar length, 13.1; mastoidal breadth, 17; interorbital 

 breadth, 7.8; maxiUary tooth row, 10.4; mandibular molar-premolar 

 row, 10. Skull of topotype (adult female): Greatest length, 32.2; 

 palatilar length, 12.8; mastoidal breadth, 16.4; interorbital breadth, 

 7.8; maxillary tooth row, 10.3; mandibular molar-premolar row, 9.9. 



Remarlcs. —Thm form is a well-marked subspecies which can be 

 separated from S. I. occultus either by skin or skull characters. Inter- 

 gradation with occultus probably occurs in the region north or west 

 of Owens Lake; a very slight indication of such intergradation is 

 noticeable in specimens of occultus from Olancha. The topotype . 

 is peculiar in that the left upper tooth row contains a supernumerary 

 premolar, apparently the one immediately posterior to the canine 

 and probably derived from the anlage of the first premolar. As is 

 the case in some specimens of S. townsendii, previously mentioned, 

 this is especially interesting, since it gives this individual one more 

 tooth than the theoretically complete mammalian dentition of 44 

 teeth. 



Specimens examined. — Two, from type locality.^ 



1 Collection Mus. Vert. Zool., Univ. California. 



