218 MONOGRAPHS OF NORTII AMERICAN RODENTIA. 



vertebrae from * to f; the hind feet, I to I; the cars are small (§ or less), 

 thin, and papery, and appear slightly hairy, but may have lost much of their 

 fur in the alcohol. The soles have but five perfect tubercles, with a minute 

 or rudimentary sixth one. 



Several skulls (as Nos Toosf, W^r 1 ) which we have extracted from 

 alcoholic specimens furnish occasion for no further comment than that they 

 are strictly of the Pcdomys type of dentition, and smaller than those of 

 austerus, in correspondence with the inferior size of var. curtains; No. 12169 

 measuring only 0.90 by O.ofi, although it is perfectly adult. 



Subgenus P1TYMYS, McMurt. 



Arvicola sp., AuCTORUM. 



= Peammomys, LeConte, 1829 (jpinetorum), (uot of Rueppill). 



— Pitymyx, McMuilTRIE, 1831 (samelype). 



= Pincmys, Lesson, 1842 (same type). 



Chars. — Below medium size; body cylindrical and otherwise shrew-like 

 in closeness and glossiness of pelage; tail very short — less than the head, 

 little more than the hind foot ; ears small, mostly concealed, sparsely pilous, 

 with flat edges, and border of meatus plane in front; feet small, both five- 

 tuberculate; fore-claws not shorter than hind-claws; palms more than half as 

 long as soles; teats only four, inguinal; skull relatively broader than usual; 

 muzzle short, very blunt; nasal branch of intermaxillary reaching beyond 

 ends of nasals ; distance from tips of lower incisors to apex of descending 

 process no greater than distance from same point to back of condyle ; first 

 under molar with only one external closed triangle and two internal ones; no 

 spur on last triangle of second upper molar; back upper molar with only one 

 exterior triangle and a posterior trefoil. 



This section, perhaps the most strongly marked among American 

 Arvicolce, nevertheless agrees exactly with Pcdomys in the dentition [i\\e 

 three diagnostic teeth, viz., front under and middle and back upper, being 

 the same), and likewise shares with Pedomys the number and position of the 

 mammae and plantar tubercles. In general cranial and external characters, 

 however, it is quite different ; Pcdomys being in these respects much like 

 Myonomes. From Chilotus, which has the same characters of the upper 

 molars, it differs in having a less number of lateral triangles on the front 

 under molar, and particularly in the. construction of the ear, as detailed else- 

 where; besides, in other external characters, Chilotus is more like Myonomes. 

 The great size of the fore feet and their claws, the small hind feet, and very 

 short tail are strong peculiarities. 



