MUSEUM OF COMPARATIVE ZOOLOGY. 229 



H. michiganensis, of which I have also had fresh specimens for examina- 

 tion, seems as well marked as any of the group, through its small size, very- 

 short tail, and dark plumbeous color at all seasons. Other specimens col- 

 lected by myself in Western Iowa, supposed from their locality to be refer- 

 able to H. sonoriensis, differ in no way appreciably, except in being a little 

 lighter colored, from average specimens of Massachusetts H. leucopus. 



H. myoides, described by Baird from Canada and Vermont specimens, is 

 positively identical with II. leucopus, the cheek-pouches — the only charac- 

 ter supposed to distinctively characterize it — being probably common to 

 all the species of the genus, as well as to Jaculus* I first became aware 

 of the existence of cheek-pouches in H. leucopus by capturing the animal 

 with the pouches distended with seeds and grain ; a subsequent examina- 

 tion of many specimens in alcohol from Berlin, Middleboro',f Springfield, 

 and other localities in Massachusetts, and from Waterville, Norway, Bethel, 

 Upton, and other places in Maine, has fully confirmed this discovery, as I 

 have yet to find the first specimen without the pouches. They almost 

 uniformly exist as described by Gapper, — that is, extending upwards to 

 the eye and posteriorly to the ear. They are equally well marked in 

 specimens of//, gossypinus and H. " cognatus," from Florida. J 



In the large proportion of equivocal species included among the thirteen 

 recognized in the General Report, to which one since described from In- 



* See antea, p. 226. 



t The Middleboro' specimens were collected by Mr. J. W. P. Jenks, and presented by 

 the Smithsonian Institution to the Museum of Comparative Zoology, labelled " Hes- 

 peromys leucopus.' 1 



{ In the Report on North American Mammals (p. 460) it is stated, "No traces of 

 cheek-pouches can be detected " in II. leucopus. Under H. myoides the same author re- 

 marks (lb., p. 472) that he found, much to his astonishment, decided indications of 

 cheek-pouches in all the alcoholic specimens of that " species " he examined. " I then,'' 

 he says, "investigated a considerable number of Middleboro' specimens, and in none 

 could I detect the slightest indication of anything of the kind." " In another specimen," 

 he says later (No. 2776), "from Watervile, New York, referable probably to the same 

 species [//. myoides], I found the cheeks crammed with large seeds, and on cutting them 

 open could see that the latter occupied a pouch of considerable size. It is possible that 

 this specimen (immature) may not belong to H. myoides, if so, we must conclude that 

 in the ability to distend the cheeks very much, even temporarily, the II. leucopus ap- 

 proaches very closely to the H. myoides, and this diminishes still more the propriety of 

 placing the latter in a distinct genus. It is quite possible that others of our species may 

 have the cheek-pouches more or less developed." It hence appears that the existence 

 of cheek-pouches in the other species of Ilesperomys was finally strongly suspected by 

 the author in question. The oversight of their presence in II. leucopus, however, is 

 somewhat surprising, since they are not difficult to discover in specimens preserved 

 in alcohol, when search for them is properly made, though in specimens badly con- 

 tracted by the alcohol they might quite readily escape observation. 



