RODENTIA GEOMYINAE THOMOMYS UMBRINUS. 



399 



In the absence of specimens of this type of Geomys from the Columbia, especially of the 

 originals of Dr. Bachman, I am unable to say whether this is identical or not with G. borealis 

 or toivnsendii, although this is quite probable. That it is the same with the Thomomys rufescens 

 of Maximilian I am satisfied, as the description agrees very well with it, the color being only 

 more yellowish, and the specimen was collected within the same region with that of Prince 

 Max. Kichardson, in his report on North American Zoology, in the .Reports of the British 

 Association, (but nowhere else,) identifies Geomys borealis with the Saskatchewan species, pre 

 viously supposed by him to be G. talpoides. Should the question of priority come up between 

 borealis and rufescens, after they are conclusively shown to be the same, it must be settled in 

 faror of the former, as having been published in the same year, but read by Dr. Bachman before 

 the Philadelphia Academy, August 7, 1838, and by Prince Max., at Breslau, January 29, 1839. 

 The species was named, but not described, by Richardson himself, in 1837. 



Several specimens of gopher, collected at the mouth of the Yellowstone, by Lieut. Warren's 

 Expedition, agree in general characters, but are smaller. The upper parts are rather light 

 yellowish brown, the sides ashy gray ; the under part, generally, grayish white ; there is a dusky 

 plumbeous tinge about the nose ; the feet and tail are white. 



List of specimens. 



THOMOMYS UMBRINUS. 



Sonora Gopher. 



Geomys umbrinus, RICH. F. B. A. I, 1829, 202. IB. Rep. British Assoc. for 1836, V, 1837, 157. 



??WATEKHOUSE, Charles. Mag. N. H. Ill, 1839, 596 ; fig of skull. 



J. L. LECONTE, Pr Ac. N. Sc. Phil. VI, 1852, 162. 

 Ascmnys umlirinw, WAGNER, Suppl. Scbreb. IV, 1843, 389. 

 Paeudostoma umbrinus, AUD. & BACH N. Am. Quad. Ill, 1851, 307. 



SP. CH. Cheek pouches large, rather sparsely haired on the outer wall. Tail slender, one-third to one-half the length 

 of body, dusky all around with a white extremity. Upper incisors convex, the groove obsolete. Hand large; claws much 

 curved, long ; middle claw 5 lines, its under surface occupying more than two-sixths of the whole hand, its digit about 

 two-eighths the same length. Claw of thumb reaching more than two-fifths over the hand. 



Color. Above, reddish brown, with a dorsal wash of very dark reddish brown ; paler on the sides and beneath. No 

 distinct mottling on the sides. Cheek pouches white inside to the margins ; edges of the mouth all round and chin dark 

 sooty brown, contrasting strongly. (No white.) 



In very old specimens, the color above is paler and more gray brown ; beneath, grayish white. 



This species is of rather small size, (judging from the specimens examined,) as compared with 

 others of the genus. The body is somewhat slender and depressed. No appreciable neck, but 

 the head apparently the termination of the trunk as usual. The fur is soft and silky lustrous ; 

 not so soft as in T. bulbivorus. The external ears are distinctly visible as an elevated 



