SCIUUID^-aPEKMOPni LUS. 



arranged all the other American Sptrmophili. He also recognized Uic highly 

 Sciurine character of the OlospermophUi, which he regarded as "only distin- 

 guishable externally by the cheek-pouches" from the true Squirrels. Colo- 

 botis, however, as thus left, embraced very diverse types. 



While, as already stated, it is impossible to subdivide the American 

 Spermophili into sharply definable groups, they admit of arrangement in 

 three sections, of which the extreme phases of differentiation are as wide 

 asunder as are most allied modern genera, but which still thoroughly inoscu- 

 late through variously intermediate specific forms. If their most differentiated 

 specific representatives stood alone, even the generic distinctness of these 

 groups would be unquestioned. An already intimated, one of these deviating 

 lines is in the direction of Cynomys, another in the direction of Tamias, and 

 the third tends strongly toward Sciurux. Provisionally recognizing these 

 sections vs subgenera, they may be characterized as follows: — 



Sabgenos Otosfbrmofiiilus Brandt (emend.)- 



Eara larKo, high, pointed (larger and more pointed thnn in aome apeciea i>f SctHma) ; tail long, 

 full, anil broad, with the haira tno-thirda to three-fonrths the length of the head and body; general 

 form of the akuU, and the dentition, atronglj Boinrine. Species, 8. grammmnu, 8. aanuIalMf. 



Subgenus Coix>boti8 Brandt (emend.). 



• 



Eara aoiall, aometimea marglniform ; tail abort, flattened, with the haira one-third to one-half the 

 length of the body ; aknll abort and broad, the zygomatic orchea broad, generally greatly widened poa- 

 teriorly ; dentition haary, and the first upper premolar generally large. Speeiea, 8. rickafd$oni, 8. empttra, 

 8. melUi, 8. ipUonma, 8. obtoletut. 



Subgenna Ictioomtb* nob. 



Eara generally amall, aometimea rudimentary; tail long, cylindrical, or narrow and flattened, or 

 quite broad, with the hairs one-half to three-fonrtha the length of the \yoAj ', aknll very long and narrow ; 

 flnt npper premolar uanally rather amall, and the dentition nr.t heavy. Species, S. tenttoautbu, 8. moci- 

 oa«M, S. MdeoemliKeatiu, 8.fmikHHi. 



In Olospermophiltts, the first upper premol-.' is scarcely larger than in 

 some species of Sciurus ; the skull is similarly nr r.hed and expanded ; the 

 anteorbital foramina are narrower, and their outer walls are thinner than in 

 the other Spermophiles. The cranial differences relate mainly to the greater 

 obliquity of the malar bone and the greater lateral expansion of the zygo- 

 matic processes of the maxillaries. S. empetra (=parryi of authors) is but a 

 little way removed from the group, and forms an easy passage to Colobotis. 



In Colobotis, the skull is shorter and broader, generally much arched, 

 the zygomatic arches more spreading, and the dentition he&vier; in all these 

 characters, as well as in the short flat tail and the thick-set form, the group 



• Ettm.— lurir ! 

 the species. 



: weasel, and /ivt » moose ; in allusion to the slender Moateline form of most of 



