SYNAPTOMYS 171 



case longer; rostrum, upper incisors and mandible remarkable 

 for breadth and massiveness. 



For exlernal and cranial tneasurenieiits, sec table at end of 

 volume. 



36. Synaptomys (Synaptomys) helaletes gossii Coues. 



1877. Arvicola {Si/naplomys) gossii Coues, Monogr. N. Amer. Rodentia, 

 Muridse, p. 235 (published as a synonym of Synaptoviya coo peri 

 but name stated to apply to specimens from Kansas, and of these 

 descriptions and measurements are printed on p. 236). 



1896. Synaptomys helaletes gossii Merriam, Proc. Biol. Soc. Washing- 

 ton, 10, p. 60; Miller, " List," 1924, p. 394. 



1897. Stpiaptnnujs cooperi gossii Rhoads, Proc. Acad. Nat. Sci. Phila- 

 delpiaia, 1897, p. 307. 



Co-tyfes.—V.^. Nat. Mus., Nos. 8464, 8508-8517; eleven 

 collected 1865-1866, by B. F. Goss. 



Type locality. — Neosho Falls, Woodson County, Kansas. 



Characters. — Similar to S. h. helaletes, but skull with longer 

 rostrum and smaller auditory bullae. 



Colour not satisfactorily known, but jjrobably more reddish- 

 brown above than »S'. h. helaletes or ;S'. cooperi. 



Skull similar to that of 8. h. helaletes but even larger, with 

 longer rostrum and nasals ; zygomata more bowed outwards 

 in the middle; orbital fossae larger. In ventral view rostrum 

 and incisive foramina conspicuously longer; post-palatal pits 

 deeper, defining a distinct median ridge which projects slightly 

 into the meso23terygoid fossa ; auditory bullae smaller, the sides 

 of the basioccipital less deeply excavated and the vacuity on 

 each side of the basisphenoid much larger. Incisors very broad 

 and heavy as in the typical subspecies ; molars nearly as large. 



For external and cranial ineasurenients, see tables at end of 

 volume. 



Subgenus: MICTOMYS True. 



1828. Arvicola Richardson, Zool. Journ., 3, p. 517 (in part). Not of 



Laccpcde, 1801. 

 1830. Lcmmus, Fischer, Syn. Mamm., p. 585 (in part). Not of 



Link, 1795. 

 1894. Mictomys True, Proc. U.S. Nat. Mus., 17, No. 999, p. 242. 



Advance sheet, April 26, 1894 (genus). 

 1896. Mictomys Merriam, Proc. Biol. Soc. Washington, 10, p. 57 



(subgenus); Miller, N. Amer. Fauna, No. 12, 1896, p. 35. 



Genotype. — Mictomys innuilus True. 



Range. — North America; in the Hudsonian Zone, from 

 Labrador to Alaska, and southwards to New Hampshire and 

 northern California. 



Characters. — Externally as in tlie typical subgenus, but 

 mammary formula 2 — 2 = 8. 



Skull with relatively slender rostrum; post-palatal septum 



