470 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 47. 



in general size and relative, as well as actual, increase in the size of 

 the ear, macrotis is very like ramona, with which it most certainly 

 intergrades. 



Specimens examined. — Total number, 22, from localities as follows: 

 Lower California: El Alamo, 1 (Field Mus.) ; Head of San An- 

 tonio River, San Pedro Martir Mountains, 1 (Field Mus., the type); 

 San Quintm, 18; Trinidad, 1 (Field Mus.); Trinidad Valley, 1. 



ONYCHOMYS TORRIDUS YAKIENSIS Merrlam. 

 1904. Onychomys torridus yahiensis Mkrriam, Proc. Biol. Soc. Washington, vol. 



17, p. 124. 'June 9. 

 1904. Onychomys yahiensis Merriam, Proc. Biol. Soc. Washington, vol. 17, p. 124. 



June 9. 



Type-locality. — Camoa, Rio Mayo, southern Sonora, Mexico, 



Geographic distribution. — Southeastern Sonora and northern Sm- 

 aloa, Mexico. Known trom the upper Rio Mayo on the north to the 

 city of Sinaloa on the south. 



General cliaracters. — Like 0. t. torridus, but larger and averagmg 

 darker in color, with larger ears and hind foot. Skull with posterior 

 border of palate never concave, rarely truncate, usually with well- 

 developed spine projectmg into interpterygoid space. 



Color. — Adult in full early winter pelage (96384, Alamos, Sonora, 

 December 19): Like corresponding pelage of true torridus, but 

 slightly darker and duller above, less rich pmkish-cinnamon ; upper 

 sides clear pmkish-cinnamon as in torridus; ears darker, thinly haired, 

 with very narrow whitish rim, and no conspicuous white lanuginous 

 tufts at bases as in torridus. Tail slightly grayish on terminal haH 

 below, brown above with whitish tip. In late winter and spring 

 (96391, Camoa, Sonora, January 17) this pelage becomes darker, less 

 bright, with large area of dull brown on upperparts and with the 

 sides more grayish-pmk, less cinnamon. Adult in short new coat of 

 late summer (95855, Camoa, Sonora, October 28; type): Upperparts 

 with broad strip of blackish-brown from between eyes to rump, blend- 

 mg into the dark pinkish-gray of sides and hips; cheeks and shouldere 

 paler; no specially developed ear tufts. Juvenile (95853, Camoa, 

 Sonora, October 28): Darker mouse-gray than young of torridus. 

 This very dark stage soon changes into a lighter coat, apparently 

 from faduig of the hairs and without moult. In this stage (96383, 

 Alamos, Sonora, December 19) the entnc upperparts are a pale drab- 

 gray, slightly darker on dorsum, against which the dark-gray ears 

 are very conspicuous in color. Post-juvenile pelage (95856, Camoa, 

 Sonora, October 28; apparently second autumn): Upperparts dark 

 brownish-gray, washed with dark rusty; ears blackish, without lanu- 

 ginous tufts at bases. This pelage moults and renews mto the coat 

 of the fully adult (96388, Alamos, Sonora, December 20), the hips and 

 posterior sides first renewing the brownish pelage of full maturity; 

 the white ear rim also becomes sharply marked. 



