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 bulle 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. 
Hypudeus rutilus var. gapperi? VIGORs. 
(Var. glareolus Sund.?) 
Arvicola gapperi ViIGoRS. Zool Journ. v, 1830. 
DEK Ay. Zool. of New York, 1842. 
SCHINZ. Synop. Mam. ii, 1845. 
| Hypudeus gapperi BATRD. Mam. N. Am., 1857. 
Arvicola fulvua 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. 
Evotomys rutilus gapperr Cougs. Proc. Acad. Nat. Sci. Phila., 1874; Monogr. 
N. Am. Rod., 1877. 
* Mus rutilus var. Pallas. 
Mus glareolus Sundeval, 1840. 
Mus glareolus Schreber. 
Hypudeeus hercynicus Mehlis, 
Arvicola rubidus Longchamp. 
Arvicola rufescens Longchamp. 
Arvicola riparia Yarrell, Jenyns. 
Arvicola pratensis Bell, Macgillivray. 
Hypudeeus glareolus Wagner. 
Arvicola glareolus Giebel. 
(H. nageri Schinz. May not belong here, it being an Alvine species imperfectly des- 
cribed.) 
