MURID^}— ARVICOLIN^— AEVICOLA AUSTERUS. 211 



Arvicola (Pedomys) austerus, Baikd, M. N. A. 1857, 539, pi. liv (teeth of specimen, No. ';"7. from Louisi- 

 ana, queried as austerus), (Wisconsin, Illinois, Missouri, and Louisiana). — Coues, Proc. Acad. 

 Nat. Sci. Phila. 1874, 190. 



Arvicola (Pedomys) tinnamomea, Baikd, op. cit. 541, pi. liv (teeth), (type, No. -f-!W, Mus. Smiths., Pembina, 

 Dak.). 



Arvicola (Pedomys) haydeni, Baikd, op. cit. 543 (type, No. •$?£*, Mus. Smiths., Fort Pierre, Dak.). 



Diagnosis. — A. ripario subsimilis, veilere austeriore, forma robustiore, 

 cauda breviore caput cequante aut paulo superante; griseo-murinus, subtus ex 

 albido plumbeus, brunneo dilute lavatus. Long. tot. 4, cauda 1.25, pedis 0.70. 



Habitat. — Western States and adjoining Territories, especially Illinois, 

 Missouri, and Michigan. Kansas. Louisiana. 



Although this animal is subgenerically different from Myonomes riparius, 

 the superficial resemblance is so close that it is difficult to convey in words 

 an intelligible notion of the distinctions. In fact, it looks more like M. riparius 

 than like Pedomys var. curtatus, from which it is not specifically different. 

 The following description is based upon about twenty specimens, mostly 

 from Illinois. 



The pelage, though not harsh, is rather coarse, thick, and short, and does 

 not lie smooth enough to possess much gloss ; a condition suggesting the apt 

 name "austerus". The tail has an average hairiness, with a medium-sized 

 pencil at tip. The ears are about flush with the fur on an average, but in 

 scant-haired specimens may overtop a little. The soles are scant-hirsute for 

 their posterior third, and 5-tuberculate, one of the tubercles of Myonomes 

 being wanting. The usual relative proportions of fore and hind feet and of 

 all the fingers and toes obtain. In general form, the animal is stouter and 

 seemingly clumsier than riparius ; the tail is shorter, averaging little more 

 than the length of the head, but sometimes reaching about one-third the whole 

 length of trunk. The head looks broader than usual, with a very obtuse 

 muzzle and rather short and sparse whiskers. 



The upper parts show an intimate "grizzle" of black, brown, yellowish- 

 brown, and grayish-brown, impossible to describe in a single word. This is 

 darkest along the middle line of the back, whence, it washes out lighter toward 

 the sides. Some specimens, as No. 2444, are almost pure black along the 

 dorsal area, and the other upper parts are correspondingly dark, showing 

 merely a grizzle with grayish-brown, without any reddish. Others, again, as 

 No. 2454, are as much lighter than the average, having no appreciably darker 

 dorsal area, and the whole upper parts and sides of a light muddy-brown 

 grizzled with brownish-gray. 



