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210 



iMONOGRAl'HS OF NOKTO AMERICAN RODBNTIA. 



of a sixth is often seen. Tlie section may readily be difTerentiated from its 

 Nortli American congeners by exclusion, thus : — It lacks the peculiar crescent 

 of the last molar of Myonomes; it wants the peculiar auricular characters of 

 Chilotus; and it has not the enlarged fore claws and glossy pelage of Pityinys. 

 The section was based upon the Arvicola austerus of LeConte by Baird, 

 who added to it two other species, A. luiydeni and A. cinnamomeus, neither of 

 which, however, is distinct. Haydeni leads into a remarkable form from the 

 plains, very different, in its extreme development, from austerus, and still more 

 unlike any other North American species. The discussion of this form is 

 presented in a subsequent article. We insert here the measurements of our 

 skulls of Pedomys, and then proceed to consider P. austerus. 



Tadlb LIII. — ileofuremnuta of nineteen akuUa o/' Pedomys austkrita. 



* l^l5!MKMl)-6e: Anlinnla not full jtrown ; niouturomenta ozolndeU f^m tfae AvornglriK- 

 t Type of einnamomtwi. ', Typo of tiaydeni. 



ARVICOLA (PEDOJIYS) AUSTERUS, LeC. 

 Prairie Meadow Moose. 



Arvicola autterue, LeContb, Proo. Acad. Nnt. 8ci. Phila. vl, 1853, 405 (Racine, Wis. ; type. No. 8849, Mns. 

 Smiths.).— AuD. & Bach., Q. N. A. iii, 1854, 289 (based on LeConte's description).— Kbnni- 

 corr, Agric. Hep. U. 8. Patent Office for 1856 (1857), 97, pi. xii, upper flg. (Illinoia). 



