﻿44 



NORTH AMERICAN FAUNA. 



[No. 10. 



Teetli. — Tlie teeth of the upper niolariform series can scarcely be dis 

 tiDguished from the corresponding teeth in 8orex personattis, except by 

 the slightly different form of the excavations on the posterior borders. 

 These excavations in S. personatns are deepest near the middle of the 

 teeth, while in 8. hoyi the deepest points are distinctly nearer the inner 

 borders. 



The unicuspid teeth of Sorex hoyi are (PI. V, figs. 6, 7) slender, deep, 

 and heavily pigmented, the colored area occupying nearly one-third 

 of the outer face of the second and third incisors, and somewhat less 

 on the canine. The second and third incisors are of equal height, 

 the second slightly the larger. The canine is about half the size of 

 the third incisor. The premolar and the fourth incisor are very minute, 

 though both are visible from the outer side. The fourth incisor is so 

 small that it is readily overlooked in alcoholic specimens or in skulls 

 that are not properly cleaned. In a specimen from Trousers Lake, 

 New^ Brunswick, both premolar and fourth incisor are remarkably large 

 (PI. Y, fig. 6), but no other specimens from the Eastern States show any 

 peculiarities to separate them from true 8. hoyi. 



The crowns of the second and third incisors, and to a less degree the 

 canine in 8orex hoyi are remarkable for the prominence of the ridge 

 forming the inner edge of the pyramidal main cusp. This ridge, which 

 is present in all species of Sorex^ is here greatly developed, and pro- 

 vided near its base with a distinct, pigmented, secondary cusp (fig. Ic). 

 This cusp is not homologous with the minute cusp on the inner side 

 of the unicuspid teeth of Blarina^ as the latter is developed from the 

 cingulnm and is near the hinder edge of the tooth, while the secondary 

 cusp in Microsorex is distinct from the cingulum and lies somewhat 

 in front of the middle of the tooth. Although the ridge which bears 

 the secondary cusp in Microsorex is not equally developed in all species 

 of true 8orex^ it is never entirely absent. It is greatly reduced in 8. 

 aranens (fig. la), 8, alpimis, and 8. richardsonij much more conspicuous 

 and sometimes even tending to form a rudimentary cusp in 8. minntus^ 

 8. personatus (fig. Ib)^ and others. 



The luandibular teeth, like the mandible itself, are remarkably short 

 and strongly built. While the individual teeth are distinctly broader 

 than in 8. personatns^ the tooth row as a whole is shorter. The teeth 

 show no essential differences in form beyond those already noticed. 



Measurements. — Unfortunately, most of the specimens of 8orex hoyi 

 that I have seen were not measured in the tlesh; hence it is imijossi- 

 ble to give satisfactory measurements for the species. An alcoholic 

 specimen from Steele County, Minn., measures: Length, 88 mm.; tail 

 vertebriB, 27 mm.j hind foot, 10 mm. Three alcoholic specimens from 

 Elk Eiver, Minn., average: Length, 81.7 mm.; tail vertebrae, 30.7 mm.; 

 hind foot, 10.7 mm. 



General remarhs. — 8orex hoyi differs so widely from other species of 

 8orex in its subgeneric characters that it needs no com])arison with any. 

 Saperficially it has much the appearance of a small, abnormally short- 

 tailed >S^. personatns. 



