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 harrisii, A. & B. No. 1600. Mohave Desert., 313 



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. 



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, Eich. 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. Vl&I. St. Louis 3V2 



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 ; f 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 h, 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. 



