RODENTIA MURINAE HESPEROMYS MYOIDES. 



473 



will not be proper to place the species in this genus. Unaccompanied by any other features of 

 external form or internal structure, the presence or absence of a cavity in the mouth can 

 scarcely be looked on as other than specific characteristics merely. 



The description and figures by Dr. Gapper, in the Zoological Journal, agree very well with 

 the specimens before me. He speaks of the species as abundant in the district of Upper Canada 

 between York and Lake Siincoe. The tail of his specimen measures 3 inches ; the body, 

 (probably stretched,) 3f . 



For an excellent specimen of this species the Institution is indebted to the Montreal Natural 

 History Society. 



In another specimen, 2776, from Waterville, New York, referable probably to the same 

 species, 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, indeed, that this specimen 

 (immature) may not belong to the H. myoides ; if so, we must conclude that in the ability to 

 distend the cheeks very much, even temporarily, the H. leucopus approaches very closely to the 

 E. 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 cheek pouches more or less 

 developed. 



The Hesperomys gracilis of Major Leconte, from Ohio, agrees very well in length of tail with 

 this species, and otherwise resembles one of the Burlington specimens. It is, however, in the 

 dried specimen, impossible to ascertain whether cheek pouches were ever present or not. The 

 tail vertebras measure 3.60 inches, 3.70 with the hairs; the body (stretched) is about 3.70. 

 The hind feet, .85. In the length of tail, so much greater than what is usual in H. leucopus, 

 I have little hesitation in referring it to the H. myoides. The specimen came from Michigan 

 or northern Ohio. 



List of specimens. 



1 Measured after being mounted. 



Original of Thompson's description of Mus leucopus. 



* Measured before skinning. 



60 L 



