138 PROCEEDINGS OF THE ACADEMY OF 



2. Thomomys clusius,' Coues, n. s. 



Char. Spec. Smallest known species of the genus ; length of an 

 adult ? about 5 inches. Feet remarkably small ; sole 0.75 ; palm, 

 including longest claw, 0.65. Fore-claws small, little curved, the 

 longest under 0.30. Tail extremely short; under 1.50 in length 

 from the true base, and little over 1.00 from the end of the conical 

 enlargement at base, the scant-haired portion being thus less than 

 one-fourth of the total length of head and body. Ears minute. 

 Color above pale yellowish-gray, with a slight brown shade, the 

 fur plumbeous at base as usual. Below, nearly pure white to the 

 very base of the fur. No dark auricular area. Feet and tail 

 white. Extremity of snout blackish. 



Hub. Type No. 3051, Mus. Smiths. Inst., Bridger's Pass, Rocky 

 Mountains, July 21, 1857, Dr. W. A. Hammond. 



1 Name, given in allusion to the characteristic habit of animals of this 

 family, of plugging up the entrances to their subterranean tunnels. 



