240 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Like that of other genera known in early zoological times, the synonymy 
of Myodes is involved. First ranged under Mus, then sharing the term 
Arvicola with the rest of its subfamily, it bas also had three names more par- 
ticularly applied to itsel/—Hypudeus (Illiger, 1811); Myodes (Pallas, 1831); 
and Lemmus (Linck, 18—). Hypudeus, as originally framed, included Mus 
lemmus, amphibius, and arvalis, and, according to some authorities, ought to 
be restricted to the first species mentioned (demmus); but, according to 
others, it is applicable to either one of the three species Illiger put in it. But 
it has of late been so carefully characterized by Keyserling and Blasius, in its 
application to Mus rutilus, &c., that if it is to be retained at all (which we do 
not think should be done), doubtless it is best assigned to ruéidus. The 
choice, then, narrows to Myodes and Lemmus; we have not the authorities 
at hand to decide the case, but the balance of opinion is in favor of AMyodes. 
Both these genera, as originally based, had a much wider application than is 
now admitted. In strict technical interpretation, both AZyodes and Lemmus 
are synonyms of Arvicola Lacépéde, 1803. Georychus Rich. Aud. is, of 
course, out of the question; Illiger’s Georychus having been based upon an 
animal of an entirely different family. . 
Recent investigations, particularly the admirable memoir of Middendorff, 
have resulted in reducing the number of nominal species of Myodes (as above 
restricted) to three—M. lemmus, M. obensis, and M. schisticolor. There is no 
question of the identity of “helvolus” and ‘“trimucronatus” of Richardson, 
Audubon, and Bachman; and nothing appears opposing Middendorff’s view 
that the North American animal (including, besides the two supposed species 
just named, M/. albigularis of Wagner) is the same as M. obensis of the Old 
World. Rather, the question is whether a still further reduction will not be 
required. It would need but a little change in coloration to transform obensis 
into demmus itself; while, regarding schisti-color, it is a suspicious circum- 
stance that here we have a nearly gray or slaty lemming, just as, in the case 
of Cuniculus torquatus, we have a gray one in what is called C. dagurus. 
The inference in this case is self-suggestive. But this is a question we do 
not propose to enter upon here; our business being simply the determination 
of the North American species. 
