MUBID^— 8IGM0DONTES— HESPEROMYS AZTECUS. 



101 



lips to share tlic white of under parts; the latter is not quite pure, owing to 

 the showing througli of the gray bases of the liairs. On tiie fore leg, the 

 color of the sides, or u darker shade, extends to tiic very wrist, there stopping 

 abruptly, leaving tiie surface of the paw wiiite (or liglit). On the outside of 

 the crus, the color of the sides, or a deeper shade, extends to the tarsus, and 

 thence on the basal third of the metatarsus; forming a sharply-defined blackish 

 area, as in H. sumichrasti, &c. This is a strong feature that never occurs in 

 true leucopus ; the rich rusty-red of the sides is liivcwise an entirely peculiar 

 shade so far as United States mice are concerned, (iiough common to several 

 Mexican species. The ears are dusky in the present stale of our specimen ; 

 tlie tail, of which less than two inches remains on (he specimen, is very 

 obscurely paler below and nearly as naked as in AIus ; but this last feature 

 may not be permanent. 



The foregoing is the adult coloration. We have no intbrmation whether 

 the young are like the adult,. or plain gray like young Iciicopm. 



Length, about 3.75 inches (0""".095, De S.); tail, averaging over 4.00 ; 

 hind foot, 0.90 ; fore foot, 0.38 ; ear, about O.fi'i high from notcii in front. 



Described from one of the three original specimens, No. .^926, Museum 

 of the Smithsonian Institution, received from M. De Saussure, and labeled in 

 what is apparently his handwriting. 



M. De Saussure's label bears the suggestive query, '^H. fexanus??" There 

 is no reasonable doubt that tlie aiimal is a subtropical offset of H. leucopus, 

 modified just as Neotoma fcrru ^mea has been; but, at the same time, the differ- 

 entiation .has proceeded sf lar that we are bound to place the animal on spe- 

 cific footing, at any rate until intermediate specimens are forthcoming. 



Since writing the foregoing, we find, as stated in another place, a number 

 of alcoholic specimens, undoubtedly referable to this species, amo"g a lot of 

 leucopus igamheli) from Cape Saint Lucas. The fact that these examples are 

 instantly distinguisliable strengtiiens the probabilities of the permanent dis- 

 tinctness of aztecus from any of the United States varieties of leu€0pus. 

 They all show a nearly naked and almost unicolor tail, and tiie peculiar exten- 

 sion of the dark color on the base of the metatarsus. A suckling young 

 appears to be gray, like young leucopus, as was to have been anticipated. 

 We cannot make out, in the alcoliol, wiietlier or not the peculiar riclnu'ss 

 ol the ferrugineous, witii very black dor.sd area, exists or not, tlie wet speci- 

 mens being indistinguishable in body-colors from the "ganibcli" that came 



«(lwi 



