NO. 2057. THE GRASSHOPPER MICE—HOLLISTER. 471 



Skull and teeth. — Skull larger than in torridus, with longer mandible. 

 The posterior border of the palate is never concave as in torridus; it 

 is rarely truncate, but usually with a very well-developed spine pro- 

 jecting into the interpterygoid space. The anterior palatine for- 

 amina are large, well bowed, and extend backward to line of the sec- 

 ond cusps of fii-st molars. The posterior palatme foramina are also 

 especially large, open, and three times as long as wide. The teeth, 

 as m all the middle Mexican forms, average larger than in the northern 

 races. (Plate 15.) 



Measurements. — Averages and extremes of seven adult specimens 

 from Camoa and Alamos, Sonora: Total length, 149 (138-156) miUi- 

 meters; tail vertebra?, 53.0 (47-57); hmd loot, 22.4 (21.5-24.0); ear 

 from notch m dry skin, 16.0 (15.2-17.8) . Skull: Condylobasal length, 

 24.0 (22.4-25.4); zygomatic breadth, 13.2 (12.4-13.5); interorbital 

 breadth, 4,5 (4.3-4.6); breadth of braincase, 11.8 (11.4-12.2); length 

 of nasals, 9.9 (9.1-10.6) ; length of mandible, 14.3 (12.8-15.1); maxil- 

 lary tooth row, 3.9 (3.8-4.0). For detailed measurements of speci- 

 mens, see page 483. 



Type-specimen. — No. 95855, United States Nat. Museum, Biological 

 Survey collection. Skin and skull of female adult (teeth moderately 

 worn), in short fall pelage. Collected October, 28, 1898, by E. A. 

 Goldman. Original number, 13158. 



Remarlcs. — Except for its large size and larger ears, yalciensis is ex- 

 ternally much like true torridus. The skull differs greatly from 

 typical torridus in the shape of the posterior border of the palate. In 

 the presence of the palatal spine it shows approach toward the some- 

 what aberrant specimens of torridus from the western limits of the 

 range of the latter, in the vicinities of Tucson and La Osa, Arizona, 

 and at Magdalena, Sonora. 



Specimens examined. — Total number, 19, from localities as follows: 



Sonora: Alamos, 7; Camoa, Rio Mayo, 11 (including the type). 



Sinaloa: Sinaloa, 1. 



ONYCHOMYS TORRIDITS CANUS Merriam. 



1904. Onychomys torridus canus Merriam, Proc. Biol. Soc. Washington, vol. 17, 

 p. 124. June 9. 



Type-locality. — San Juan Capistrano, Zacatecas, Mexico. 



Geographic distribution. — Zacatecas, Aguas Calientes, and south- 

 western San Luis Potosi, Mexico; south and east to Rio Verde, San 

 Luis Potosi. 



General characters. — Closely related to 0. t. yalciensis, but differing 

 greatly in color; less bright cinnamon or brownish, more pinkish-gray. 

 Greatly resembles in color the San Joaquin Valley form, 0. t. tularen- 

 sis. Seasonal changes in pelage very slight. 



Color. — Adult in full winter pelage (82102, Rio Verde, San Luis 

 Potosi, January 13): Upperparts wood-brown, everywhere washed 



