SCIDKID^— SYNOPSIS OF GENEUA. 



041 



III. Skoll kborl, broad, and ronndail ; pootorbltal prnrcKWii well dovclnpcd, Hicnder, dirpoted dowmrnrd 

 and backward ; lygoinatio arobM niually slendi<i . t he malar cxpuiidrd In a nearly vertical plane, 

 •oinetlmcs turned sIlBhtly oatward doraally ; aiitcoiliital foramen a narrow alii, untt'rior to Ibu 

 xyK0iK*tic proceaa of the maxillary ; npper premolara eltber (wo or one (two an n rule) ; when 

 two are preMDt.tbe flnt iaalwaya aniall and aomutiuiva deciduous; cam uiuderuto, well clotbcd, 

 and lometimca coupicuoualy tutted ; no clieek-poncbca ; nail of pollex rudimentary ; pelagn 

 Henerally ooft, bat occaiiooally coarse and more or leu rigid ; tail broad, witb tbe baira mostly 

 directed laterally Sciurti: 



TV. Skull, in general form, intermediate between tbat of Soiarat and Tamiat ; iMwtorbital proceaaea 

 smaller, and tbe nasal bones narrower (at least Iban in Seitirv); no cbeek-poncbea ; ears very 

 omall or rndlmeniarjr ; tail abort, but sligblly flattened; pelage barsb, consiatiDg of flattrned, 



grooved spines and coarse bristly bairs, witb little under fur Xerut. 



V Skull narrowed anteriorly ; postorbital procetses very slender, directed downward and backward ; 

 lygonwtie arobes more expanded and depressed anteriorly, and tbe plane of expansion of tbe 

 molar more obllqnt; anteorbltal foramen oval, situated In tbe bsseof tbe zygomatic process 

 of the maxillary ; upper premolars either two or one ; when two are present, tbe first is gener- 

 ally minnte ; large intemitl cheek-poncbrs ; ears of mi dinm size, well clothed, but never tufted ; 

 poliaz with ■ well developed nail ; tail rather broad, but shorter and much narrower than 

 in aetartu and joiwopfems; pelage soft ; dorsal surface witb longitudinal stripes; sizo rather 

 ■mall Tamia*. 



Vt. Skull variable in form, being either narrow ?nd elongate or short and broad, much as in Sciurtu ; 

 poatorbital prooessea gunerally triangular, strong, and directed downward ; zygomatic process 

 of the maxillary depressed and expanded ; plane of tbe malar bone turned outward, sometimes 

 expanded nearly horizontally; zygomatie arches spreading; auteorbital foramina placed 

 more anteriorly than in Taaii«(, much as in Beiurui, but rather larger and more circular, 

 with a strongly developed tubercle at the outer lower border; npper premolars always two 

 tbe first variable in size, but always Isrger than in the preceding genera, in some species rela- 

 tively nearly as large as in <'|f»osiys ; grinding-teeth in some species nearly as in Sdarat, in< 

 ereasing in size in other species till nearly as strong ss in Cgnomni; cheek-pouches well devel- 

 oped ; body slender or thick-set ; tail long, moderate, or short ; ears large, medlnm, or mdiiuent- 

 ary, never tufted ; nail of pollex generally rudimentary ; character of the pelage and pattern of 



ooloration variable Spermopkiliu, 



VII. Skull atroDg and massive, rather short and broad ; zygomatic arches widely expanded ; malar 

 rather slight, Its plane oblique ; mnzzio narrow ; postorbital processes long, strong, and directed 

 downward ; anteorbltal foramina rather large, snbtriangnlar, thrown outward basally, and 

 placed well forward ; npper premolars two, tbe first large, of the same breadth antero-posteri- 

 orly as the other grinding-teetb ; dentition very heavy, tbe grindiug-teelb witb the trausverae 

 breadth twice tbe antero-poaterior, tbe last molar much larger than tbe others, and snbtriangn- 

 lar ; the molar series strongly convergent posteriorly; body heavy, thick-set; cheek-pouches 

 not large; tail short ; ears radimentsry i oall of po'lex well developed ; pelage short and rather 



harsh Cyaomyn. 



VIII. Sknil with the dorsal outline nearly straight ; trontiU region flat or depressed ; in other res|iects 

 the form is much as In Cpumjft, but with heavier: postorbital processes, not (or but slightly) 

 deenrved, mnoh weaker dentition, and the molar varies parallel ; interparietal and occipital 

 crests much more strongly developed than in tbe ov'ier genera; size large; body stout, broad, 

 depressed ; oheek-ponehes absent or small ; tail short, bushy ; ears small ; nail of pollex broad, 

 flat; pelage coarse, heavy... ^ Aniomii: 



In the first fire genera, the skull is more or less convex above, being in 

 tbe first three highly arched, but generally much less so in Spermophilus, and 

 still less in Cynomys, while in Arctomys it is nearly straight. The postorb- 

 ital processes become much heavier in Cynomys than in the preceding genera, 

 but reach still greater development in Arctomys. The skull is generally des- 

 titute of ridges for muscular attachment, but such ridges are generally trace- 

 able in aged individuals, even in Sciurus, in which, however, they are- widely 



separated, converging posteriorly. In most of the Spermophiles, they are more 

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