1852.] 161 



B. Dentes primores sulco medio nullo. 



6. G. rufescenB, raoUipilosus, saturate cinereus, supra rufo-tinctos,lateribus 

 et infra albo-tinctus, oribus brevibus, cauda mediocri albo-pilosa, primoribus 

 superioribus intus marginatis. 



Large. Small. 

 Length from nose to root of tail, ... 8* 5*4 



" Tail, 1-9 2- 



Fore foot to end of third claw, ... 1. -8 



Hind foot to end of third claw, . . . 1-15 '9 



Thomomys rvfescens Weid, Nov. Act. Leop. Car. Akad. (1839) 19, 3Y7 ; 

 Schinz, Syn. Mam. 2, 134. 



Geomys horealis Bachman, Journ. Ac. Nat. Sc. (1839) 8, 103 ; Richardson, 

 Report British Ass. 2, 150 ; Schinz, Syn. Mam. 2, 136. 



Geomys Toivnsendi Bachman, Journ, Ac. Nat. Sc. 8, 105 ; Richardson, Zool. 

 of Beechey's Voy. 12 ; Schinz, Syn. Mam. 2, 137. 



?OryctOTnys (Saccophorus) Bottce Eydoux, Voy. Favorite, (1837) 1, 2, 23. 



Ascomys rufescens Wagner, Schreber Saiigeth. Suppl. 3, 387. 



Ascomys borealis Wagner, ibid. 391. 



Ascomys Townsendi Wagner Wagner, ibid. 391. 



Pseudostoma borealis, Aud. & Bachm. Quadr. Am. 3, pi. 142. 



Saccophorjcs borealis Gray, Cat. Brit. Museum, 142. 



" Geomys bursarius Richardson." Gray, ibid. 



Two specimens from Columbia river, J. K. Townsend; the larger one labelled 

 "Pseudostoma Townsendi (Rich.)," the smaller one "Pseudostoma borealis." 



The fur is very fine and shining, dark cinereous, tipped on the back with ru- 

 fous, on the sides and beneath with white; on the chin and feet the hair is almost 

 entirely white. The whiskers are gray, and nearly as long as the head. The 

 ears are short but distinct. The tail is covered with whitish hair ; the upper in- 

 cisors are slender, and marked with a very fine line at the inner margin of the 

 anterior face. 



This species (and probably all the others of this division,) has the inferior 

 incisors much more slender than those above described ; the fossorial claws of the 

 anterior feet are also much smaller, so that even if the teeth were wanting no 

 difficulty would ensue in the determination of the species. 



The specimen of the Prince de Weid was found on the plains of the Missouri, 

 but his description agrees so accurately with our specimens, that there can be no 

 doubt of their identity. Dr. Bachman mentions his want of faith in the specific 

 difference of the two specimens described by him, and gives them as distinct on 

 the authority of Richardson. The latter remarks in Beechey's Voyage, that 'G. 

 Townsendi is distinguished from G. borealis by its longer tail." It must be ob- 

 served, however, that in Dr. Bachman's measurements, the small specimen of G. 

 borealis, five inches and a half in length, has the same length of tail as the large 

 one, which is two inches longer. The specimen of G. Townsendi of the same 

 size as the large G. borealis, had a tail nine lines longer, which is in exact pro- 

 portion to the small specimen of G. borealis. The large specimen now before 

 me, (which is labelled G. Townsendi,) has the precise proportions of the G. 

 borealis described by Bachman, and is probably the identical one examined bj 

 him. On careful examination, I find that the tail does not taper regularly as in 

 the other specimen, and, moreover, at its apex a distinct cicatrix is visible. I 

 think we are therefore warranted in concluding that Geomys borealis is founded 

 in a mistake. 



I do not know what Mr. J. E. Gray means by quoting " Geomys bursarius 

 Richardson, Report of British Association, 1836, 156," as a synonym of this 

 species. Sir John Richardson, on page 9 of the Zoology of Beechey's Voyage, 

 mentions that Mus bursarius of Shaw is a Geomys, and on page 12 describes G. 

 borealis, thereby implying that he considers them as distinct species. 



There is a third specimen in the museum of the Academy labelled " Pseudos- 

 toma Richardsonii, Columbia river, J. K. Townsend," which only differs from 



