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MONOGRAPHS OK NORTH AMEUICAN RODENTIA. 



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logardcil. Tlic mpusiireinonts given hnyond arn taken from the skins, and 

 socni lo indicate n form nearly as large as the S. carolinensis from the South 

 Allantir- and Gulf States; yet, on comparison of specimens, the feet of the 

 Miridii s|ieciinons prove to be much smaller, the head narrower and every 

 way smaller, showing in reality a much smaller animal, not much exceeding 

 in siz(! S. hudsonius. The New Leon specimens, however, are fairly inter- 

 mediate, lacking the fulvous tint of the sides seen in northern specimens, and 

 in general color and character of the pelage considerably approach the Merida 

 examples. • 



De [-jaussuro describes 8. carolinensis as a Mexican species, and Tomes 

 gives it as inhabiting Guatemala. De Saussure's description indicates an 

 animal not very different from the northern 8. carolinensis, including the 

 fulvescent sides and centrally rufous tail. The "cauda corpore vix brevior" 

 and the size show the animal is not referable to 8. coUiai. This seems to 

 indicate the extension southward of the habitat of 8. carolinensis throughout 

 Mexico to Yucatan and Guatemala, its range southward being thus coexten- 

 sive with that of Lfpus sylvaticus, L. palusiris, and L. aquaficus. 



GENERAL KEMARK8 ON 8CIUBU8 CAROLINENSIS AND ITS VARIETIES. 



Differential characters. — Vars. leucotis and carolinensis cannot of 

 course be trenchantly defined On comparing specimens from New England 

 with others from Florida, representing, of course, the pxtremes of variation, the 

 differences between the two, both in color and size, are very striking; but, in 

 passing southward from Massachusetts to Florida, this wide difTerence is found 

 to be effected by gradual and im])erceptible steps. In New England specimens, 

 a large proportion arc wholly without a central dorsal area of brown; in Penn- 

 sylvania, Ohio, Illinois, and Iowa specimens, it is a pretty constant feature, 

 varying greatly, however, in extent with different individuals. In Eastern 

 Pennsylvania and Maryland specimens, this brownish dorsal area becomes 

 more extended, but the sides of the body, and generally the rump, are still 

 strongly washed with whitish. Carolina specimens, especially from the coast 

 region, strongly approach the Florida ones. The few specimens before me 

 from the Gulf States render it probable that the form existing there differs 

 little from the extreme phase lA' carolinensis as developed in Florida. The 

 variation in size is equally gradual, consisting of a decrease in size southward. 

 The dividing line between the habitats of the two forms may perhaps be 



