28 U. Ss. P. R. R. EXP. AND SURVEYS—ZOOLOGY—-GENERAL REPORT. 
Dimensions of the skull. 
8. cooperi. 8. platyrhinus. 
Ie — — —_ 
' 
633 634 635 636 | 1694 1697 
| 
Skull, length ....__-_-- OG Sees AAC SP | ac il | .65 . 69 
Shonlli widths 22 S| ee eel Soe RE gn america pee? - 30 
Length of palate -_---.-- Od) ae ee a2 |\|Seasso se - 26 - 25 
Width of upper jaw----|  .15 “15 715 ~15 -15 15 
This species is closely allied to the S. personatus, having the same general form and color. 
It is somewhat larger, however, and the tail longer in proportion, nearly equalling the head 
and body. In some respects it resembles S. coopert of Bachman, as in the size, color, and 
length of tail. It differs from the description, however, in having very distinct and well- 
defined ears, and in having only three true molars below instead of four. This latter character, 
however, if actually existing in S. coopert, is entirely unique among the shrews, the invariable 
formula being 2 anterior incisors, 2-2 lateral teeth, and 3-3 molars, making 12 teeth in the whole 
jaw. The external ear, too, may readily have shrunk in drying so as to be inconspicuous, and 
thus give rise to the impression of its absence. In some dried skins before me there is little 
indication of ears, while they are very distinct in well prepared specimens, and especially in 
those preserved in alcohol. The size of the hind feet and the longer tail show that it is not the 
same with the specimen from Fort Union, at the mouth of the Yellowstone, (S. haydent). 
The skin described by Dr. Bachman was obtained in the ‘‘Northwest Territory,’’ either 
Wisconsin or Minnesota. From the list of localities it will be seen that several are recorded 
from these regions, all agreeing essentially with those from New York. Indeed, it is the only 
small long-tailed of the group, having 32 teeth, yet received from Wisconsin and Minnesota. 
After some hesitation I have come to the conclusion that the Sorex cooperi is distinct from the 
species so abundant in Massachusetts, and described by Dekay as Otisorex -platyrhinus. It is 
appreciably smaller, with an absolutely longer tail and muzzle, the former much more hairy, 
especially at the tip. The skull is longer and more slender ; the upper premolars are not im- 
bricated anteriorly, but are distinct, though in contact, the points directed downwards, and even 
a little backwards. The 3d and 4th premolars are nearly or quite equal, and less than the 
1st and 2d, instead of lessening gradually. 
As this species is very closely allied to two others of the same group, it may be as well to 
present here the principal characters of all, before proceeding to describe the remaining ones. 
For the type of S. cooper, I have taken a specimen of the smaller variety, with the longer tail ; 
the larger one is still more distinct. 
S. cooperi.—Head very long, over 8-tenths of an inch; ears conspicuous, not concealed ; 
head and body nearly two inches long; tail vertebra generally over 14; tail slightly swollen 
towards the middle; hind foot 0.45 of an inch; teeth light chestnut. 
Above, light chestnut brown, more fuscous in winter. Beneath, whitish. 
S. haydeni.mHead moderately long, under 8-tenths of an inch; ears large, but concealed 
