MUSEUM OF COMPARATIVE ZOOLOGY. 185 



11. Spermophilus spilosomus, Bennett. Sonoran Spermophile. 



Eleven spociniens, representing both the young and the adult, are in the col- 

 lection from San Luis Potosi, and one each from San Pedro (Coahuila) and 

 Parras. There is very little variation in color with age or individually. 



" Abundant. Lives on the open plains and about the edges of fields, where 

 it is a troublesome pest. Hibernates. Many are tamed." 



12. Cynomys ludovicianus (Ord), Baird. Eastern Prairie Dog. 

 Five specimens, from the vicinity of Saltillo. "Only a single small colony 



was met with, in a little valley surrounded by mountains, not far from Saltillo, 

 confined to an area of some thirty or forty acres." 



This discovery extends the range of the species considerably to the south- 

 ward and eastward of any point from which it has hitherto been reported. In 

 " Monographs of North American Rodentia," p. 896, I inferentiaUy gave its 

 southern limit as the Staked Plains of Western Texas, overlooking the fact 

 that it had been recorded by Dr. Kennerly (Rep U. S. Mex. Bound. Surv., IL 

 Mamm., p. 40) and by Duges (La Naturaleza, I. p. 137) from the State of 

 Chihuahua, the former observing it as far westward as the Sierra Madre. 



13. Mus decumanus, Pallas. Brown Rat. 



" Abundant in the cities of the interior, as well as in those of the coast. It 

 was common at San Luis, and extends as far north at least as Zacatecas." 



14. Mus alexandrinus, t,t. Geoffroy. 



Four specimens, from San Luis, where it is " common in the houses." In 

 addition to these are two specimens which seem to be unquestionably hybrids 

 between this species and M. rattus, with which it has been repeatedly stated to 

 interbreed. 



15. Mus rattus, Linne'. Black Rat. 



Two specimens, San Luis Potosi. " Lives in the houses and also in fields." 



16. Mus musculus, Linne'. House Mouse. 



" A numerous pest everywhere in the houses." 



17. Hesperomys melanophrys, Coues. 



One specimen, a full-grown male, San Luis Potosi, September 1, 1879. 

 " Rather common in the fields." 



As admitted by both Coues (North Amer. Rodent., p. 102) and Alston 

 (Biol. Cent. Amer., Mam., p. 147), there is strong probability that H. mela- 

 nophrys, Coues, and H. mexicanus, De Sauss., are identical. The specimen col- 

 lected by Dr. Palmer agrees in size with Dr. Coues's largest examples from 

 Tehuantepec ; the black eye-ring is also quite conspicuous, but the back pos- 

 teriorly is apparently more strongly ferrugineous. I therefore provisionally 

 adopt Coues's name in preference to De Saussure's. 



