NATURAL SCIENCES OP PHILADELPHIA. 195 



characters need not be here recapitulated. The several ascribed 

 species of North American Myodes proper are reducible to the 

 following, which is not specifically separable from that of Asia. 



1. Myodes obensis, Brantz. 



Syn. Myodes obensis, Brantz, Muisen, 1827, 55. Keys, and Bias., Werb. 



Eur. vi. 1840, pp. vii. and 32. Midd., Sib. Reise, ii. 1853, 99, pi. ii. 



figs. 7, 8, 9, pi. viii. pi. ix. and pi. x. f. 2. Baird, M. N. A., 1857, 



559. 

 Arvicola (Georychus) helvohis, Rich., F. B. A., 1829, 128. 

 Georychus helvolus, And. & Bach., Q. N, A. iii. 1853, 84, pi. cxx, f. 1. 

 Myodes helvolus, Dall, Alaska and its Res. 1870, 577. 

 Arvicola {Georychus) trimucronaius, Rich., App. Parry's 2d Voyage, 



1825, 309 ; F. B. A. i. 1829, 130. 

 Georychus trimucronatus, And. and Bacli., Q. N. A. iii. 1833, 86, pi. 



cxx. f. 2, 3. 

 Myodes trimucronatus, Dall, Alaska, 1870, 577. 

 Myodes albogularis, Wagner, Suppl. Schreber, iii. 1843, 602. 



Hah. More western portions of Arctic America. 



Ohs. Of this species I have handled about forty specimens, the 

 first examined by an American naturalist for many years. They 

 differ somewdiat from the only two Siberian skins before me, pos- 

 sibly representing a variety (to be called Myodes helvolus) ; but I 

 am far from disputing Yon Middendorff's decision as to their 

 specific identity with the Asiatic animal. 



Genus IX. CUNICULUS, Wagler. 



Stn. Mus, Arvicola, Myodes et Lemmus, Auctt. Georychus, partim. Rich., 

 And. and Bach., nee lll.Cuniculus, Wagler (" 1880"), Isis, 1832, 

 1220; type C gr(enlandicus= G. torquatus or Jiudsonius. Lilljeborg, 

 Syst. Ofvers. Gnag. Glires, 1866 (same type). 



Obs. Withont going into the characters of a perfectly well- 

 known form, I wish to particularl}^ signalize the fact that this 

 genus, tliough 'based upon a " lemming," is very different fi'om 

 3Iyodes^ and, indeed, from any other arvicoline type. The molar 

 pattern is strongly of an ordinary arvicoline general character 

 not at all as in Myodes or Synapfomys wliile details of the molar 

 dentition (as, for instance, six prisms on back upper molar and 

 nine on front lower molar) are unique. The obsolete ear and 

 pollex, the singular hypertroph}^ of the two middle fore claws, and 

 the notable seasonal changes of pelage, are all peculiar. I find 

 but one American species, identical with that of Asia. A second 

 supposed species, C. lagurus, I have not seen. 



