194 BULLETIN NO. VII. 



into distinct prisms. The faces of the upper molars especially 

 present less complicated figures than usual; instead of alter- 

 nating triangles we find single irregular figures extending 

 entirely across the tooth. The skull is very broad and is 

 greatly inflated in the perotic region, the auditory bullse being 

 larger than in any other mouse. The bony palate is broad- and 

 rather short and abruptly truncate at the posterior nares ( not 

 with a second shelf before reaching the basis cranii). The 

 pterygoids are not very prominent. The cranium is large 

 while the facial portion is greatly reduced and the interorbital 

 distance is quite small. The posterior extremity is propor- 

 tionally large but there are no indications of either saltatorial 

 or fossorial capacities. 



It has been shown by Dr. Coues that in America we have but 

 a single species of this genus, H. rutilus Pallas, which occurs 

 in its typical form throughout the Arctic portions of the con- 

 tinent. It is thus seen that H. rutilus, like so many Arctic 

 animals is circumpolar in distribution and has become modi- 

 fied southwardly so as to give rise to varieties which may be 

 diverse in the western and eastern hemispheres. The southern 

 varieties have been called gapperi in America and glareolus* in 

 Europe, there being nothing to show them distinct. 



Hypudaeus rutilus yar. gapperi? VIGORS. 



(Var. glareolus Sund.?) 



Arvicola gapperi VIGORS. Zool Journ. v, 1830. 



DEKAY. Zool. of New York, 1842. 

 SCHINZ. Synop. Mam. ii, 1845. 

 Hypudceus gapperi BAIRD. Mam. N. Am., 1857. 

 Arvicola fulva AUDUBON and BACKMAN. Journ. Acad. Nat. Sci. Phila. 



viii, 1842. 



WAGNER, Wiegmann's Arch., 1843. 

 Arvicola dekayi AUD. and BACK. Quad. N. Am. iii, 1854. 

 Ewtomys rutilus gapperi COUES. Proc. Acad. Nat. Sci. Phila., 1874; Monogr. 



N. Am. Kod., 1877. 



*. Mus rutilus var. Pallas. 



Mus glareolus Sundeval, 1840. 

 Mus glareolus Schreber. 

 Hypudceus hercynicus Mehlis, 

 Arvicola rubidus Longchamp. 

 Arvicola rufescens Longchamp. 

 Arvicola riparia Yarrell, Jenyns. 

 Arvicola pratensis Bell, Macgillivray. 

 Hypudoeus glareolus Wagner. 

 Arvicola glareolus Giebel. 



(H. nageri Schinz. May not belong here, it being an Alpine species imperfectly des- 

 cribed.) 



