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MURID4—ARVICOLINA—ARVICOLA. 
two exterior closed triangles, wo interior closed triangles, and a small sub- 
circular posterior trefoil, all of which makes a very different pattern from 
that presented by A. riparius. Another skull, from Siberia, labeled “obscurus” 
(No. 3226), shows an anterior loop, three external closed triangles, two internal 
closed triangles, and a posterior trefoil that is almost a short, very coneavo- | 
convex crescent by the depth of the notch of its inner leaflet. This is nearer 
to A. riparius, but not exactly it, as there is an additional interior closed tri- 
angle, and the crescent is not quite a crescent. A close approach, however, 
is made by No. 3228, labeled “decoriorum? or e@conomus?” from Siberia; and 
in another, No. 2026, labeled ‘‘agrestis”, from Sweden, the peculiar pattern 
of riparius is exactly reproduced. Upon dental characters alone, there- 
fore, we would take as the name for our riparius any special genus that has 
been proposed upon either of these last-named species. The external char- 
acters, however, of riparius, do not agree with those short-tailed forms of 
boreal Europe and Asia, such as agrestis,* wconomus, &c., but are very nearly 
as in “‘ratticeps”. We, therefore, think it probable, as we said above, that the 
section for which we adopt the name Myonomes is not exactly represented in 
Europe, and consequently less confusion can ensue if we reject for the species 
not only Hemiotomys, but any other generic name that may have been based 
upon-an Old World form. All the subgeneric or even “generic” divis- 
ions that we know of in the genus Arvicola are (with the single exception 
of the strongly-marked Hypudeus of Keyserliung and Blasius and of Baird, 
equal to our Evotomys) so trivial as to be, in fact, but slightly superspecific 
designations, only worthy of being retained on the score of usefulness ; for it 
is practically a convenient thing, in so difficult a genus as Arvicola, to strike 
* If the Central and Southern European specimens of “arvalis” and the northern ones of “agrestis” 
be correctly labeled, there appears to be some mistake in what Professor Baird says (/. ¢. 513), in speaking 
of the species of his section Hypudeus. ‘“Arvicola arvalis of Southern Europe,” he says, “and Arvicola 
agrestis of Northern Europe, supposed to be identical with the A. arvalis of authors, fall legitimately in 
the other genus” [i. ¢., in Arvicola proper instead of in Hypudus]. But all our skins marked “arvalis” 
have the prominent ears, &c., of “ Hypudeus”, and their skulls have the peculiar palatal structure of “Hypu- 
deus”, and their molar teeth are rooted, with crowns exactly as in other “ Hypudwi”. They certainly are 
Hypudeus (Evotomys), and must be ranged close alongside ZL. rutilus, LE. rubidus, £. glareola, and E. gapperi. 
Oa the other hand, those skins marked “agrestis” have the hidden ears and short tail and other exter- 
nal characters, and the ordinary bifossate palatal structur , of Arvicola proper, to say nothing of their 
rootless molars, with crowns fashioned nearly as in riparius. So far, then, are our specimens from being 
specifically identical, that they are not even congeneric. We do not know how it may be with the 
“arvalis of authors”, not having looked up the bibliography of the species; but, certainly, the “arvalis” 
before us is not as Professor Baird supposed. 
On a subsequent page (516), however, Professor Baird correctly says that “4. agrestis from Sweden, 
in the character of its skull and teeth, belongs strictly to the group having 4. riparius for the type”. So 
the mistake seems to be simply in confusing ‘ arvalis” with agrestis. 
