10G ZOOLOGY. 



Pinemys, Lesson, Nouv. Tabl. R. A., 1812, 12 (type pinetorum). 

 Eemiotomys, Bi>., ]M. N. A., 1857,515 (type A. riparius, Oed). 

 Pedomys, Bn., <>]>. tit., 517 (type A. austerus, LeC). 

 Chilotus, Bb., op. o7., 510 (type A. oregonus, BAcn.). 



The four sections into which the North American species of this difficult 

 genus fall may be thus distinguished : 



A. Back upper molar with 2 external triangles and a posterior crescent. 



Middle, upper molar with 2 internal triangles. Front lower 

 molar with 3 internal and 2 or 3 external lateral triangles. 

 Ears unrinuiied in front. Soles O-tuberculate. Fore claws not 

 longer than the hinder ones. Tail about ^ the length of head 

 and body, or more. Pelage ordinary. Size maximum and 

 medium Myotomes. 



B. Back upper molar with only 1 external triangle and a posterior trefoil. 



Middle upper molar with 1 internal triangle. Front lower 

 molar with 3 internal and 2 or 3 external triangles (as in 

 Myonomes). Ear with a rim in irout of meatus, the anterior 

 and posterior roots of the auricle there meeting. Soles 5-tuber- 

 culate (?)■ Fore claws not larger than the hinder. Tail about 

 $ the head and body. Pelage ordinary. Size minimum Chilotus. 



C. Back and middle upper molars as in the last. Front lower molar with 



only 2 internal and 1 external triangle. Ear nnrimmed. Soles 

 5-tubercnlate. Fore claws not larger than the hinder. Tail $ 

 the head and body, or rather less. Pelage ordinary. Size 

 medium Pedomys. 



D. Molars all as in Pedomys. Ears nnrimmed. Soles 5-tuberculate. Fore 



claws larger than the hinder. Tail about \ the head and body, 



or less. Pelage dense, silky, moledike. Size small Pitymys. 



Subgenus MYONOMES, Raf. 



Arvicola of most American writers. 



Arvicola, A, Hemiotomys, Baied, M. N. A., 1857, 515 (type riparius. Not of Selys-L.). 



Myonomes, Raf., (type M. pratensis, Bat., based on " Wilson's Meadow Mouse" = 



A. pennsylvanica, Ord. = A. riparius, Ord). — Coues, Proc. Acad. Nat. Sci. 



Phila., 1871, 189. 



ARVICOLA (MYONOMES) RIPARIUS, Ord. 



Campagnol or Meadow Mouse of Pennsylvania, Waeden, Descr. U. S., v, 025. 



Meadow Mouse, Wils., Am. Orn., vi, pi. 50, f. 3. 



Arvicola pennsylvanica, Okd, Guthrie's Geog., 2d Am. ed., ii, 1815, 292 (based on the 



foregoing).— HAELAN, Fn. Am.. 1825, 144(in part; quotes Ord, but describes 



pinetorum). 

 Arvicola riparius, Oed, .1. A. N. S. P., iv, 1825, 305 (Philadelphia). 

 Arvicola riparius longipilis, Kenn., Agric. Rep. U. S. Patent Ofiice, 1850, 301 (West 



North field, HI.; in winter pelage). 



