1894.] NATt^RAL SCIENCES OF PHILADELPHIA. 287 



mondi to a place in nomeuclature. It may lie stated that Richard- 

 sou's A. novebonicen^ls (Raf. ), the name under which that author 

 described the type of flntmmondi was said by him to have come from 

 the dry uphmds of tlie Rocky Mountains inhabited by A. .noithog- 

 nathus. This woukl indicate a locality far north of that from which 

 ray specimens came, also a less aquatic environment, and a somewhat 

 ditierent faunal region. Audubon and Bachman give, * ' Valleys of 

 the Rocky Mountains," as the habitat of dnonmondi. More com- 

 plete collections from the whole length of the intermediate country 

 may show that the Lac La Hache animal is separable from the 

 northern one ; in such an event the name microcephahis may still be 

 applicable to it. 



Arvicola (Mynomes) drummondi. Topotype Xo. 418, arl. ^. Coll. of S. X. 

 Elioads; Lac La llacbe, B. Columbia, Juuc 30th, 1892. Vol. })y S. N. E. 



Description. — Size considerably less than that of A. pennsijlvan- 

 icus; ears moderate ; tail short and scantily haired ; skull small, 

 highly arched, compressed and elongate, the orbits much narrowed 

 liy the compression of the zygoma ; eyes very small, as in Pitymys ; 

 feet as originally described by Richardson. Teeth of typical Mynomes, 

 the postero-internal section of middle upper molars as large as its 

 opposing outer triangle. Color above grizzled black-brown, beneath 

 a clear hoary plumbeous, lacking the muddy wash mentioned by Aud. 

 and Bach. Tail sooty above, grayer beneath. 



Measurements. — Total length, 155 mm; tail vertebrae, 40; hind 

 foot, 20 (average of four adults — Total, 153 ; tail, 39; foot, 19). 

 ►Skull — Total length, 24-2 ; Jia-silar length, 22 ; zygomatic width, 

 13-5; length of nasals, 6-6; incisor to post-palatal notch, 12-2; inter- 

 orbiial constriction, 4 ; length of mandible, 14-8; width of mandible, 

 8-2. 



This species resembles A. nanus,^ but its possession of a five 

 triangled middle upper molar distinguishes it from that species, 

 which, as Dr. Merriam expressly states, has but four triangles. The 

 two specimens from Field show no differences from the one above 

 described. 



Incidental to this rather cursory study of the principal group of 

 North American Arvicolince it is worthy of mention that the large 

 vole captured by Mr. Drummond " at the foot of the Rocky Moun- 



' Merriam, N. Amer. Fau., No. 5, 1891, 63. 



