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NORTH AMERICAN FAUNA. 



[^o. 12, 



Feet. — The soles are moderately Lairy. They have five well-devel- 

 oped tubercles, but uo trace of a sixth. The claws are well developed 

 ou all the feet, those ou the front feet either equaling or exceeding 

 those on the hind feet. 



Ill M. pinetorum the front feet are much larger and tlie front legs 

 shorter than in true Microtus. These peculiarities are less developed 

 in subterraneus and J/, saril. Of the other species 1 have not seen 

 alcoholic specimens, and so am unable to say which of those mentioned 

 they most closely resemble. 



Fur. — The fur in all the known species is remarkably short and dense. 

 This character is most noticeable in M. pinetoruni, which lias an almost 

 mole-like coat. 



Miscellaneous characters. — The tail, eyes, and external ears are much 

 reduced in all the species of Fitymys. These characters, as well as the 

 peculiarities of the fur and front feet, are distinctly adaptive and fit 

 the animals for their underground life. 



General remarlcs. — While Fitymys agrees with Fedomys inthe number 

 of mammas and footpads, it is readily distinguished by its highly mod- 

 ified fur, small eyes and ears, and flattened skull. The tyj^e and most 

 extremely developed species is further characterized by its greatly 

 shortened front legs. 



Fitymys is represented in America by Microtus plnetorum (Le Conte) 

 and several forms related to 2L quasi ate r (Cones). In Europe a num- 

 ber of species and subspecies occur. Among these the best known 

 are M. subterraneus (De Selys Longchamps) and M. savii (De Selys 

 Longchamps). 



Subgenus CHILOTUS Baird. 



1857. ChilofHS Baird, Mamm. N. Am., p. 516, 1857. Type, Arvicola oregoni Bacliman. 



Geographic distribution of type species. — Oregon, Washington, and 

 British Columbia. 



Geographic distribution of subgenus. — The range of the subgenus 

 Chilottis is coincident with that of the type and only known species. 



Fssential characters : 



Palate normal. 



m 3 normally without closed triangles. 



m 1 with 5 closed triangles and 9 or 10 salient angles. 



m 3 with 2 or 3 closed triangles and 6 salient angles. 



Mammas 8. 



Plantar tubercles 5. 



Sole moderately hairy. 



Claws on hind feet longest. 



Fur short and dense. 



Sl-ull— The skull of Chilotus (PI. I, fig. 8) is low and flat, the dorsal 

 outline nearly straight, and the brain case not widened, as in Fedomys. 

 As coini^ared with Fedomys^ the rostrum is remarkably long and slender 

 in proportion to the rest of the skull. 



