MUEIM3— ARVICOLIN^— ARVICOLA. 



155 



£wo exterior closed triangles, two 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 concavo- 

 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 azconomusV 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,* ojconomus, &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 Hypudceus of Keyserling 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 " aroalis " and tbe northern ones of "agrestis" 

 be correctly labeled, there appears to be some mistake in what Professor Baird says (/. c. 513), in speaking 

 of the species of his section Hypudaius. "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. c, in Arvicola proper instead of in Hi/pudwus}. But all our skins marked "arvalis" 

 have the prominent ears, &c, of " Hypudccus ", and their skulls have the peculiar palatal structure of "Hypu- 

 dceus", aud their molar teeth are rooted, with crowns exactly as in other "Bypudan". They certainly are 

 Sypudaus (Evotomys), and must be ranged close alongside E. rutilus, E. rubidus, E. glareola, and E. gapperi. 

 On 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, tho "arvalis" 

 before us is not as Professor Baird supposed. 



On a subsequent page (516), however. Professor Baird correctly says that "A. agrestis from Sweden, 

 in the character of its skull and teeth, belongs strictly to the group haviug A. riparius for the type ". So 

 the mistake seems to be simply in confusing " arvalis " with agrestis. 



