Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
EXPLANATION OF THE PLATES. 
2—Sciwrus cinereus, L.—Fox squirrel.—No. 932.—Washington, D. 6 AS pean 
References a-e, as in fig. 1. 
3—Spermophilus harrisii, A. & B.—No. 1600.—Mohave Desert.¢...........sseeeeeeee 
a-e as in fig. 1; /—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. 
1—Arctomys monax, Gmelin.—Woodchuck.—No. 1261.—Western Missouri....... 
Skull natural size ; a—e as in the preceding plate. 
2— Aplodontia leporina, Rich.—Sewellel.—Puget’s Sound..........sccsescssesseeeeeeees 
Natural size ; a-e as in the last; view of occiput from behind. 
PLATE L. 
1—Geomys clarkii, Baird.—No. 1623.—Presidio del Norte...........csccsecceseeeseeees 
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; 
j—lower jaw from above; g—lower molars of the left side, magnified. 
2—Geomys bursarius.—Gopher.—No. 1767.—St. Louis..........cceccssssseeeeereeeeeeee 
References as in fig. 1. 
3—Thomomys bulbivorus.—California Gopher.—No. 1280.—Monterey, California 
References as in fig. 1. 
PLATE LI. 
1—Dipodomys ordii, Woodh.—Kangaroo rat.— Western Texas.......ssscssscsereees ' 
Skull. All the outlines three times the natural size ; a—skull from below ; 
‘6—skull from above ; c—skull from the side; d—left side of lower jaw; 
e—left side of lower jaw from above ; f—occiput from behind. 
2—Dipodomys ordii; Woodh.—No. 1125.—Sonora, Mexic0.....ssssecscecsseeeseesceees 
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; 7, g, h, magnified about twice. 
3—Perognathus monticola, Bd.—No. 1585.—St. Mary’s, Rocky mountains......... 
Quite old; references a—h, as in the last figure; /, g, and h, magnified 
nearly three diameters. 
4— Perognathus hispidus, Bd.—No. 1695.—Matamoras..........sccceecscsscceeeeseeeeees 
Male ; teeth not worn; references a—g as in preceding. 
PLATE LI. 
1—Thomomys bulbivorus.—California gopher.—No. 1280.—Monterey, California. 
Skull. References a-g as in fig. 2, plate LI ; fand g magnified two diameters. 
2—Geomys breviceps, Baird. —No. 1138.—Prairie Mer Rouge.........ccscseeeeereceeee 
References a-g, as in preceding figure; f and g magnified about three 
times. 
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