544 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
posterior triangle, two internal, one external, and an anterior lobe indented on each side so 
deeply that the enamel nearly meets ; there is also a shallow indentation anterior to these on 
each side. There are thus five distinct salient internal angles, four external, and a slight addi- 
tional one on each side of the loop anterior to the others. 
This species is rather larger than the Arvicola austera. It differs from it also in the more 
bristly character of the hair. Theears are shorter and broader. The colors differ considerably 
in a prevailing grayer tint above. The cheeks are much lighter, as is also the side of the 
muzzle. The under parts are whiter, the light tips being longer; they are without the 
cinnamon tinge of the other species. The feet are whiter. 
In some respects this species seems to approach the A. drummondii. The latter, however, is 
said to have the tail shorter, (one inch,) and the prevailing color above, a brownish gray tinged 
with red. In the A. haydeni, however, the tail is 1} inch long, and the prevailing color grayish 
yellow brown, without any tinge of red or chestnut whatever. 
List of specimens. 
te 
©) Measurements. 
G] 
2 = 
s (8 e)z] . i 
5 nS 3 Locality. When col | Whence and how | Nature of} & | | S/S | E |e " | i Collected by— 
Be sa Se lected. obtained. specimen. | 3 | 3 | z Flan % s/2]/8 
o/s : Zz) Sie 
&|/2 |¢ glelelelelsl2ls1 8 
ci ee le 2/PleleleBlels) 2/2 
= ° s s = | =) 
Sa Sate zizlelelmlalajala 
699'| 1862 | GQ | Fort Pierre, Nebraska| 1854.......| Col. A. Vaughan...) Skin...... 1.25/4.50/1.50)1.60 1,14 65. «-|-eee| Dr. F. V. Hayden. 
ecvveslevcces|cccsleces nse nessarsestse nerve cece lcccnccccecescnnetees|sspeesesecce| pee 4.25)1.40)1.55) .81 . ; 40] 135)... cece veceeeceeee 
* The first line gives the measurements taken before skinning ; the second, those of the dried skin. 
ARVICOLA (PITYMYS) PINETORUM, Leconte. 
Psammomys pinetorum, Lecontr, Annals N. Y. Lyceum, III, 1, 1829, 132; pl. ii. 
Pitymys pinetorum, McMurrnie, Cuvier, R. A. Amer, ed. Appendix, I, 1831, 434. 
Pinemys pinetorum, Lesson, Nouv. Tabl. R. A. 1842, 12. 
Arvicola pineorum, Auv. & Bacu. N. Am. Quad. I, 1851, 216; pl. Ixxx. 
Lecontr, Pr. A. N. Sc. Phila. VI, 1853, 409. 
Arvicola scalopsoides, Aun. & Baca. J. A. N. Sc. Phila. VIII, m, 1842, 299. (Long Island.) 
Waener, Wiegmann’s Archiv, 1843, m1, 53. 
? Lecontg, Pr. A. N. Sc. Phila, VI, Oct. 1853, 409. 
? Arvicola apella, Leconte, Pr. A. N. Sc. Phila. VI, 1856, 405. 
Sp. Cu.—Length, 3} inches. Body elongated; head obtuse, short. Ears concealed, rounded, less than half the hind 
foot, covered with short, close hairs, Antitragus nearly obsolete. Tail shorter than the head. Fre feet large, three-fourths 
as long as the hinder, shrew-like ; fore claws longest. Hind feet six-tenths of an inch long. 
Fur short, close, lustrous; about one-fourth of an inch long. Above, dark, clear, chestnut brown; paler on the sides ; 
beneath, hoary plumbeous. Feet light brown. Tail pale rufous beneath. 
Skull, . 95 by .58, or as 100 to 61. Muzzle rather short; its projection beyond the root of the zygoma less than the 
length of the line of upper molars. 
Body cylindrical, narrow, and elongated. Head short and blunt. Whiskers shorter than 
the head ; mixed black and gray. Eyes very small. Ears short, nearly orbicular, but broader 
