210 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
of a sixth is often seen. The section may readily be differentiated from its 
North American congeners by exclusion, thus: —It lacks the peculiar crescent 
of the last molar of Ayonomes ; it wants the peculiar auricular characters of 
Chilotus; and it has not the enlarged fore claws and glossy pelage of Pitymys. 
The section was based upon the Arvicola austerus of LeConte by Baird, 
who added to it two other species, A. haydeni 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. 
TABLE LIII.— Measurements of nineteen skulls of PEDOMYS AUSTERUS. 
2 % a Erom tip of un- | 3 a a 
Width at— 5 ic der ees to— 5 5 2 . 
‘ , He E | lieu 4 q a 3 ae 
2 Locality. fe st % = a aa sly ee 
5 Wc lees |) Bedell Bie seal ae |p erste 8 2 
A A ss) N oS |8 A ie} 3 |A A A i) 
BAG Eracine WWilssccesseccsseec=e cee 1.00 | 0.40 | 0.60 | 0.17 | 0.23 | 6.20 | 0.60 | 0.75 | 0.80 | 0.22 | 0.33 | 100: 60 
248 5 0.24 | 0.20 | 0.58 | 0.75 | 0.77 | 0.24] 0.33] 100: 60 
0.25 | 0.21 | 0.67 | 0.93 | 0.87 | 0.27] 0.38] 100: 58 
0.23 | 0.19 | 0.65 | 0.81 | 0.84 | 0.24 | 0.36 
0.24 | 0:17 |...... 08754 ee 0.24 | 0.32 
ae 0.63 | 0.78 | 0.80 | 0.25 | 0.33 
0.20 | 0.62 | 0.81 | 0.82} 0.25 | 0.33 
0.25 | 0.68 | 0.65 | 0.89 | 0.24 | 0.39 
0.21 | 0.64 | 0.78 | 0.80 | 0.25 | 0.35 
seeeed0ss 
Saint Louis, Mo 
0.18 | 0.62 | 0.74 | 0.81 | 0.25 | 0.33 | 100: 59 
a2 Seas os 0. 
1687 | Caleasieu, La..-..-...-..------- AOS) (O45 eee 0.18 | 0,22 | 0.19 | 0.62 | 0.77 | --~..| 0.23 | 0.30 
iz14}| Pembina, Dak ....-.------------ 1.12 | 0.40 }.-..-. 0.17 | 0.25 | 0.20 | 0.65 | 0.82 | 0.83 | 0.23 | 0.32 
| 1A8A2t] Fort Pierre, Dak...-..-.---.---. 1.14 |,0.45 | 0.65 | 0.18 | 0.25 | 0.19 | 0 66 | 0.80 | 0.87 | 0.26 | 0.34] 100: 57 
JV AER) Sone ocsecosacos7 1069|\eene 0. 62 
* 12159-60-61-68: animals not fall grown; measurements excluded from the averaging. 
+ Type of cinnamomeus. t Type of haydeni. 
ARVICOLA (PEDOMYS) AUSTERUS, LeC. 
Prairie Meadow Mouse. 
Arvicola austerus, LECONTE, Proc. Acad. Nat. Sei. Phila. vi, 1853, 405 (Racine, Wis.; type, No. 2249, Mus. 
Smiths.).—Aup. & Bacu., Q. N. A. iii, 1854, 289 (based on LeConte’s description).—KENNI- 
corT, Agric. Rep. U. 8. Patent Office for 1856 (1857), 97, pl. xii, upper fig. (Illinois). 
