408 [October^ 



Pennant with the Arv. agrestis of Europe. It is very easily distinguished from 

 any otiier of the genus that I have seen in America, by the furrow on the inner 

 margin of the superior incisors, and by the large antitragus of the ear, which 

 completely closes up the auditory passage as with a valve, the last character 

 showing that it is peculiarly fitted for an aquatic life. It is generally pointed 

 out by American naturalists as the A. xanthognathus of Leach, a species which 

 I have never had the good fortune to see, and which I scarcely believe has ever 

 been found for from the Arctic regions. As for its habits, it delights in marshy 

 places, and swims and dives with much dexterity. It leaves the lower grounds, 

 however, and is often found in upland meadows. Formerly it was very common 

 in the vicinity of New York. This was before the advance of population on that 

 favored spot had destroyed everything connected with nature, except the vices 

 of man. 



There is generally quoted in connection with this species of Arvicola, a figure 

 in Wilson's Ornithology, vol. vi., pi. 50, which has nothing characteristic about 

 it, and may as well be said to represent anything else. 



8. Arvicola borealis. Capite magno et obtuso, auribus brevibus, sub pilis 

 occultis. Tarso subtus dense piloso. Cauda sparse pilosa, supra nigrante, sub- 

 lus fusco cinerea. 



Hab. In provinciis borealibus. (R. Island, Mr. Powel.) A. borealis Rich., 

 1. c. p. 127. VViegman's Archiv., 1843, part 2, p. 53. Schinz., 1. c, p. 251. 

 Wagner, 1. c. 593. 



Hair very shining, dark plumbeous, above and on the sides tipt with bright 

 brown and black, so as to have a somewhat variegated appearance, beneath with 

 gray very slij^htly tinged with brown. Head large, short and blunt ; ears round, 

 entirely concealed under the fur, hairy both within and without; antitra<:us large, 

 semicircular. Feet light cinereous brown, covered with short shining hair, the 

 tar?i beneath densely hairy; thumb tubercle, with a short, straight blunt nail. 

 Tail thinly covered with hair, above dusky, beneath brownish grey. 



Length in. 62 ; head 1-3 ; ears "25 ; foreleg -9 ; hind leg 1-7 ; tail 2. 



9. Arvicola californicus. Subvariegatus rufescenti-fusco et nigro. Corpore 

 brevi et robusto, pilis speciem hirsutiei habentibus, revera tamen mollibus et 

 levibus. Auribus submagnis, pene sub pilis occultis. Cauda supra fusca, sub- 

 tus fusco-cinerea. 



Hab. In California. A. Californica Peale, Zool. Expl. Ex. Quadrupeds, 46. 



Body short and thick. Hair rather long, very shining, at the roots plumbeous 

 black, above and on the sides tipt with reddish brown and black in such a man- 

 ner as to give it a hirsute appearance, which in reality it does not possess, be- 

 neath with grey. Head blunt; ears rather large, almost concealed under the fur, 

 hairy both within and without. Feet covered with short shining, greyish brown 

 hair; thumb tubercle, with a compressed blunt nail. Tail above brown, beneath 

 cinereous brown. 



Length 5-7 ; head 1-3 ; ears '46 ; fore leg 1 ; hind leg 1*5 ; tail 1-5 ; fur '45. 



The dentition differs from that of A. riparius as follows : In the upper jaw the 

 second interior triangle of the first tooth is furnished with a small, sharp poste- 

 rior lobe, and the interior triangle of the second has likewise a sh?rp posterior 

 lobe, fn the lower jaw the first tooth is formed of 8 triangles, 1 anterior, which 

 may rather be called an oval, 1 posterior, 3 exterior and 3 interior. The line of 

 teeth in the upper jaw differs in having internally 9 salient and 9 re-entering 

 angles, and in the lower jaw in having externally 10 salient and 9 re-entering 

 angles, and internally 12 salient andll re-entering angles. 



10. Arvicola occidentalis. Pilis mollissim's et tenuissimis, extremitatibus 

 superioribus rufis sine ulla nigri admistione. Auribus sub pilis occultis. Cauda 

 sub comprcssa, supra et subtus concolore rufa. 



JIab. In territorio Oregonensi. A. occidentalis Peale, 1. c, 45. 



Hair dark plumbeous, very soft and fine, above tipt with bright rufous without 

 any admixture of black, beneath with grey. Head blunt ; cars round, entirely 

 concealed under the fur, hairy only on the outside ; antitragus rather shorter than 

 usual. Feet covered with short shining, ru'ous hair; thumb tubercle, with a 



