1910.] 



CrXOMYS MEXICANUS. 



21 



80 per cent of the skulls examined from the two extremes are readily 

 determinable. The very slight average increase in size and the 

 shghtly more vinaceous summer coat are of such trivial degree that 

 alone they would be valueless as characters for subspecific separa- 

 tion. Throughout southeastern Arizona and over most of the New 

 Mexican range of the form the skull characters are well marked, but 

 in western Texas such a strong tendency toward C. I. ludovicianus 

 appears as to make identification of single specimens or unsatisfac- 

 tory series virtually impossible. I have therefore considered the 

 range of the form restricted to the region from the Pecos Valley 

 south and west, where 75 per cent or more of the skulls are deter- 

 minable. The area of intergradation with the subspecies ludovi- 

 cianus is so extensive (from Texas to Nebraska) that it is really 

 larger than the range of either subspecies in its typical form. 

 Specimens examined. — Total number, 184, as follows: 



Arizona: Bonita, 1; Dos Cabesos, 1; Dragoon Summit, 1 (cotype);^ FortHua- 

 chuca, 10; Huachuca Plains, 4; Point of Mountain, 4 (including cotype);^ 

 San Pedro River, Mexican Boundary Line, 20; * Sulphur Spring Valley, 2; ^ 

 Willcox, 13. 



Chiliualiua: Colonia Juarez, 5; Juarez, 2; Sierra en Media, 1. 



New Mexico: Animas Valley (Grant County), 14; Cactus Flat (20 miles north 

 of Cliff), 4; Capitan Mountains, 3; Cliff, 1; Cloverdale, 3; Dog Spring (Grant 

 County), 9; Faywood, 2; Gila (Grant County), 1; Hachita, 2; Jornada del 

 Muerto, 1; Lake Valley, 3; Lone Mountain, 1; Manzano Mountains (east foot- 

 hills), 2; Organ City, 1; Playas Valley, 1; Queen, 3; Roswell, 2; San Luis 

 Springs (=Lang's ranch, Grant County), 26 (including 17 odd skulls); San 

 Pedro, 3; Santa Rosa, 7; Silver City, 5. 



Texas: Alpine, 1; Altuda, 3; Belen (El Paso County), 4; El Paso, 4; Fort Davis, 

 1; Guadalupe Mountains (near), 1; Limpia Mountains (=Davis Moun- 

 tains), 1; Pecos River, 1; Presidio County, 2; Sheffield, 3; Sierra Blanca, 5 



CYNOMYS MEXICANUS Merriam. 

 Mexican Prairie-Doq. 

 (PI. I, fig. 3; PI. II, figs. 3, 5; PL V, fig. 3; PL VII, fig. 2.) 

 1892. Cynomys mexicavus Merriam, Proc. Biol. Soc. Washington, VII, p. 157, July. 

 Type locality. — LiSl Ventura, Coahuila, Mexico. 

 GeograpMc distribution. — Southeastern Coahuila and northern San 

 Luis Potosi, Mexico. North to Saltillo; south to Vanegas. 



Characters. — Size of Cynomys ludovicianus, but with longer tail; 

 coloration above in summer coat less reddish, more grayish and 

 vinaceous-buff, and much more heavily Hned with black; coloration 

 in winter still more hoary; black on terminal portion of tail much 

 more extensive; teeth smaller. 



1 Collection Amer. Mus. Nat. Hist. 



2 Collection Mus. Comp. Zool. 



3 Collection Field Mus. Nat. Hist. 



< Dr. Mearns tells me that a few of these specimens were actually collected on the Mexican side of the 

 boundary line, in Sonora. 



