EXPLANATION OF THE PLATES. 
747 
Page. 
Fig. 2 —Sciurus cinereus, L.—Fox squirrel.—No. 932.—Washington, D. C...... 248 
Eeferences a-e , as in fig. 1. 
Fig. 3 —Spermophilus Jiarrisii, A. & B.—No. 1600.—Mohave Desert.*. 313 
a-e as in fig. 1 ; f —left upper molars from below, (inverted by the en¬ 
graver ;) g —left lower molars from above. The two last figures magni¬ 
fied nearly three times. 
PLATE XLIX. 
Fig. 1 —Arctomys monax, Gmelin.—Woodchuck.—No. 1261.—Western Missouri. 339 
Skull natural size ; a-e as in the preceding plate. 
Fig. 2 —Aplodontia leporina, Rich.—Sewellel.—Puget’s Sound. 353 
Natural size ; a-e as in the last; /—view of occiput from behind. 
PLATE L. 
Fig. 1 —Geomys clarkii, Baird.—No. 1623.—Presidio del Norte. 383 
a —under view of skull; b —upper view of skull; c—the same from the side; 
d —upper molars of the left side, magnified ; e —lower jaw from the side; 
/—lower jaw from above; g —lower molars of the left side, magnified. 
Fig. 2 —Geomys bursarius. —Gopher.—No. 1767.—St. Louis. 372 
References as in fig. 1. 
Fig. 3 —Thomomys bulbivorus .—California Gopher.—No. 1280.—Monterey, California 389 
References as in fig. 1. 
PLATE LI. 
Fig. 1 —Dipodomys ordii , Woodh.—Kangaroo rat.—Western Texas.. 410 
Skull. All the outlines three times the natural size ; a —skull from below ; 
b —skull from above ; c—skull from the side ; d —left side of lower jaw; 
e —left side of lower jaw from above ; /—occiput from behind. 
Fig. 2 —Dipodomys ordii, Woodh.—No. 1125.—Sonora, Mexico. 410 
Another skull, natural size; a-e as in the preceding figure; /—upper 
molars from below ; g —left lower molars from above ; h —upper incisors 
from the front; /, g, h, magnified about twice. 
Fig. 3 —Perognathus monticola, Bd.—No. 1585.—St. Mary’s, Rocky mountains. 422 
Quite old ; references a-h, as in the last figure ; /, g, and Ji, magnified 
nearly three diameters. 
Fig. 4 —Perognathus hispidus, Bd.—No. 1695.—Matamoras. 421 
Male ; teeth not worn ; references a-g as in preceding. 
PLATE LII. 
Fig. 1 —Thomomys bulbivorus .—California gopher.—No. 1280.—Monterey, California. 389 
Skull. References a-g as in fig. 2, plate LI; /and g magnified two diameters. 
Fig. 2 —Geomys breviceps, Baird.—No. 1138.—Prairie Mer Rouge. 378 
References a-g , as in preceding figure; / and g magnified about three 
times. 
