Description of a New Prairie Dog. 157 



DP]SCR1PTI0N OF A NEW PRAIRIE DOG (CYNOMYS 

 MEXICANUS) FROM MEXICO*. 



BY DE. C. HART MERRIAM. 



In ^larch, 1891, ]Mr. Clark P. Streator collected a series often 

 skins and skulls of Prairie Dogs at La Ventura, in tlie extreme 

 southeastern corner of the Province of Coahuila. ^lexico, 220 

 miles south of Laredo, on the boundar}- betAveen Texas and 

 Mexico. Mr. Streator writes that the colon}' from which these 

 animals were obtained was the largest he had ever seen. The 

 species proves to be new. It resembles the common Prairie Dog 

 of the Great Plains (C ladovicianus), but differs from it in l)eing 

 somewhat larger and in having a much longer tail. The tail 

 differs further from that of any known Prairie Dog in the extent 

 and intensity of the black on the terminal portion. The black 

 covers the distal half below and forms a sulnnarginal band 

 around the terminal half above, being both more extensive and 

 blacker in color than in liidoririanvs. 



The new species may be known l)y the following description: 



Cynomys mexicanus sp. iiov. 



Type No. lUtUl ^ ad. U. S. National Museum (Department 

 of Agriculture Collection). From La A^entura, Coahuila, Mexico, 

 Mar. 24, '91. Collected by Clark P. Streator. (Original No. 625.) 



Measurements. — -Total length, 419; tail vertebra^, 107 ; hairs, 

 24 -h [worn off at tips] ; hind foot, B3. 



General Characters. — The largest species of the genus ; similar 

 to Cynowys liulovictanus, l)ut larger, with longer and blacker tail. 



Ci)lor. — Upper parts everywhere grizzled butfy-fulvous, si)arsely 

 mixed with long black hairs; under parts and feet huffy. Tail 

 above: concolor with the back, Init with abroad suljmargiual 

 band and tip of ]:)lack, which reaches back more than half the 

 length of the tail. Tail l)elow : proximal half buffy like belly, 

 washed with fulvous ; distal half black, grizzled with l)uffy, from 

 the color of the basal part of the hairs, which shows through. 



The type specimen has not completed the spring molt, and 

 the posterior two-thirds of the back is pale rufus from the wear- 

 ing away of the light tips of the hairs, bringing the subapical 

 rufus zone to the surface. ]\Iost of the specimens have com- 

 pleted the molt. 



* Read before tlie Biological Society of Washington, May 14, 1892. 



