yO PATAGONIAN EXPEDITIONS: ZOOLOGY. 



Genus AKODON Meyen. 



Akodon Meyen, Nov. Act. Acad. Caes. Leop. -Carol., XVI, 1833, 599- 



Type, Akodon boliviense Meyen, sp. nov. 

 Acodon Tschudi, Fauna Peruana, Mamm., 1844, 177. Emendation of 

 Akodon. — Thomas, Ann. & Mag. Nat. Hist. (6), XIV, Nov., 1894, 

 360. "Syn. Habrothrix, Waterh. 1837." 

 Abrothrix Waterhouse, P. Z. S., 1837, 21 (subgenus of Mus). Type, 

 Mus [^AbrotJirix) longipiUs \\'aterh., sp. nov. — Gray, Cat. Mam. Br. 

 Mus., 1843, 114 (full genus). — Thomas, P. Z. S., 1884, 450 (sub- 

 genus oi Hesperoniys); P. Z. S., 1896, 1020 (full genus). 

 Chelemys Thomas, Ann. & Mag. Nat. Hist. (7), XII, Aug., 1903, 242 

 (subgenus of Akodon). Type, Hcsperomys mega/onyx Waterhouse. 

 The genus Akodon, as currently limited, includes nearly one hundred 

 species, covering quite a diversity of forms, which differ in size, te.xture of 

 pelage, coloration, and proportion of parts, and it will doubtless be found 

 advisable to divide the group, when better known, into a number of sub- 

 genera, although in cranial and dental characters there is great uniformity 

 of structure, and no very evident lines of division. In general they are 

 heavy-bodied, short-limbed, short-tailed, vole-like mice, with ears small 

 to medium, pelage generally soft and full but sometimes short and velvetv, 

 and claws of ordinary size or strongly developed and fossorial. The color 

 above varies from mouse-gray to dark brown, with or without reddish 

 brown on the back, or nearly uniform dark yellowish brown ; the ventral 

 surface varies from white or whitish gray to dark gray, or, as in the A. 

 caliginosiis group, to nearly as dark as the color of the back. In the A. 

 pulcherrimus group there is a distinct pattern of white markings on the 

 sides of the head, nearly enclosing the ears. The species vary in size 

 from the size of a house mouse to that of the larger species of Microtus. 

 The teeth vary little in structure, but very much, relatively, in size, some 

 of the fossorial forms, like A. niacronyx, having much heavier dental 

 armature, relative to the size of the animal, than the A. xanthorhtnus 

 group. 



Sufficient material is not at present available for a critical revision of 

 the group, which evidently may be divided for convenience into several 

 fairly well-marked sections, characterized mainly by external characters. 

 Mr. Thomas has already separated the big-clawed Akodonts as a sub- 



