MURID^— ARVICOLINiE— ARVICOLA. 



155 



two exterior closed triangles, (wo interior closed triangles, and a small sub- 

 circular posterior trefoil, all of which makes a very dilferent pattern from 

 that presented by A. riparim. Another skull, from Siberia, lal)eleil '^ohxcurus" 

 (No. 322G), siiows 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 leallet. 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 "decoriomm? or aconomus?" from Siberia; and 

 in another, No. 2026, labeled "tigresds", from Sweden, tiie i)eculiar pattern 

 of riparius is exactly reproduced. Upon dental characters alone, there- 

 fore, we would take as the name for our ripariux 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 agrentis,* aconoiiius, &c., but are very nearly 

 as in "ratticeps". We, therefore, think it probai)le, 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 Hemiotonujs, but any other generic name that may have been based 

 upon an Old World form. All the sui)generic or even "generic" divis- 

 ions that we know of in the genus Arvicola are (with the single exception 

 of the strongly-marked Hypudicus of Keyserling and Blasius and of Baird, 

 equal to our Evotoynys) so trivial as to be, in fact, but slightly superspecifie 

 designations, only worthy of being retained on the score of usefulness; for it 

 is practically a tfonvenient thing, in so difficult a genus as Arvicola, to strike 



* If tbo Central and f.oiitherti Enropeau speciuHiHB of "arvaU» " ami tbe iiortliorn ones of " agreotis" 

 bo correctly liibcled, tbero appears to be soino mistake in wbat Professor Baird says (/. c. 513), in speakin"; 

 of the species of his section Ilijpndwuii. "Arvicola ar%'alis of Suntbern Europe," bo says, "and Airimla 

 agrmtit of Nortbern Eiirupu, supposed to bo identieal with the A. atra(i» of authors, fall le^-itiniit ,ely in 

 tbo other genns" [i. e., in Arvicola proper instead of in lli/piidceus]. Bnt all our skins marked "arralit" 

 have tbe proniincut ears, &c.,of " Ilijpudaui ", and their skutU have tbo peculiar palatal structure of "ZA/pii- 

 da:m", and their molar teeth are rooted, with crowns exactly as in other " Hiipudnl". They certainly are 

 Hypuda'm (ErolomyH), and must be ranged clcse alongside E. rutilm, E. nibidas, E. glareola, and E. gapperi. 

 On tbe other hand, those skins marked " agrestis " have tbe bidden ears and short tail and other exter- 

 nal characters, and the ordinary bifof..-,ite palatal strnctnr , of Arrieola prupcr, to say nothing of their 

 rootless molars, with crowns fashioned nearly as in ripariun. So far, tlien, are our specimens from being 

 specifically identical, that they are not oven congeneric. Wo do not know bow it may lie with tbe 

 "arralin of authors", not having looked up the bibliography of tbo spociesj but, certainly, the "arvalis" 

 before us is uot as Professor Itaird 6up|H)sed. 



On n subsequent page (.MO), ...iwever, Professor Baird correctly says that "A. agreetit from Sweden, 

 in tbo character of its sknll and teeth, Vielongs strictly to tbe group having A. ripariiu for the type ". So 

 tbo mistake scorns to be simply in confusing "arrafi*" with agreaiin. 



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