LIST OF ILLUSTEATIONS. XIII 



Page. 

 Fig. 41. — Sciurus griseus anthonyi. Laguna Mountains, California, a, Fore- 

 foot; b, hindfoot 265 



42. — Sciurus griseus anthonyi. San Diego County, California, o, Dorsal 



view; b, ventral view; c, lateral view 266 



43. — Sciurus apache. San Luis Mountains, near Monument No. 65. a, 



Dorsal view; b, ventral view; c, lateral view 272 



44. — Sciurus arizonensis huachuca. Huachiica Mountains, Arizona, a, 



Dorsal view ; b, ventral view ; e, lateral view 278 



45. — Sciurus rufiventer texianus. Dorsal view of skull. Fort Clark, 



Texas 282 



46. — Sciurus rufiventer. Dorsal view of skull. West Northfield, 



Illinois 282 



47. — Eutamias dorsalis. a, Dorsal view; b, ventral view; c, lateral view. 290 

 48. — Ammospermophilus harrisii saxicola. (Type.) a. Dorsal view; b, 



ventral view ; c, lateral view 307 



49. — Callospermophilus lateralis. San Francisco Mountains, Arizona, a, 



Dorsal view; b, ventral view ; c, lateral view 310 



50. — Citellus tridecemlineatus. Fort Snelling, Minnesota, a, Dorsal 



view ; b, ventral view 327 



51. — Citellus tridecemlineatus. Fort Snelling, Minnesota 328 



52. — Citellus mexicanus parvidens. (Type.) a. Dorsal view; 6, ventral 



view ; o, lateral view 329 



53. — Citellus spilosoma arens. Fort Hancock, Texas, a, Forefoot; b, 



hindfoot 331 



54. — Citellus spilosoma macrospilotus. La Noria, Sonora, near Monu- 

 ment No. 112. a, Dorsal view; b, ventral view; c, lateral view... 334 



55. — Citellus tereticaudus. Quitobaquita, Arizona 337 



56. — Cynomys ludovicianus arizonensis. a, Dorsal view ; b, ventral view ; 



c, lateral view 340 



57. — Castor canadensis frondator. (Type.) a, Dorsal view; b, ventral 



view ; c, lateral view 351 



58. — Mus alexandrinus. a, Skull; h, upper molai's; c, lower molars 363 



59. — Mus musculus. a, Forefoot; b, hindfoot; c, ear; d, tail 364 



60.— Onychomys'longipes. o, Skull; &, lower molars: c, upper molars.. 370 

 61. — Onychomys pallescens. a, Skull; b, lower molars; c, upper molars. . 371 



62. — Onychomys melanophrys. a, Lower molars; 6, upper molars 373 



63. — Onychomys torridus. a, Forefoot; b, hindfoot; c, tail 375 



64. — Onychomys torridus. a, Lower molars; b, upper molars 375 



65. — Onychomys torridus arenicola. Skull of type, a, Dorsal view; b, 



ventral view ; c, lateral view 377 



66. — Onychomys torridus perpallidus. Skull of type, a, Dorsal view; 



b, ventral view; c, lateral view - 378 



67. — Baiomys taylori. Under surface of feet. «, Forefoot; 6, hindfoot.. 381 

 68. — Baiomys taylori. Crowns of molar teeth showing progressive stages 



of wear, a, c, and e, Lower series; 6, d, and/, upper series 381 



69. — Baiomys taylori. Skull. «, Dorsal view; 6, ventral view; c, lateral 



view 382 



70. — Peromyscus sonoriensis. a, Dorsal view of skull; b, crowns of lower 



molars; c, crowns of upper molars 385 



71. — Peromyscus sonoriensis rufinus. Skull, a, Dorsal view; b, ventral 



view ; c, lateral view '. 393 



72. — Peromyscus sonoriensis rutinus. Crowns of molar teeth, a, Lower 



series; b, upper series 393 



