Genus—ABROCOMA.[[37]]
Dentes primores ²⁄₂ acuti, eradicati, anticè læves: molares utrinque ⁴⁄₄ subæquales, illis maxillæ superioris in areas duas transversales ob plicas vitreas acutè indentatus divisis; plicis utriusque lateris vix æquè profundis; illis mandibulæ inferioris in tres partes divisis, plicis vitreis his internè, semel externè indentatis, areâ primâ sagittæ cuspidem fingente, cæteris acutè triangularibus.
Artus subæquales.
Antipedes 4–dactyli, externo brevissimo, intermediis longissimis et ferè æqualibus.
Pedes postici 5–dactyli; digito interno brevissimo. Ungues breves et debiles, illo digiti secundi lato et lamellari; omnibus setis rigidis obtectis.
Caput mediocre, auribus magnis, membranaceis; oculis mediocribus.
Cauda breviuscula.
Vellus perlongum, et molle.
The genus Abrocoma is evidently allied on the one hand to the genera Octodon, Poephagomys, and Ctenomys, and on the other to the family Chinchillidæ. The four genera just mentioned possess so many characters in common, that it would be well to unite them, and the name Octodontidæ may be used to designate the group.
The Octodontidæ appear to bear the same relations to Echimys, as the Arvicolæ do to the Muridæ.