MUKID^-ARVrCOLIN^— ARVICOLA PINETOKUM. 219 



Back under molar with three spherical-triangular dentine islands in 

 single series reaching across the tooth. Middle under with posterior spher- 

 ical triangle; then interior closed triangle; then exterior closed triangle; 

 then two angles generally confluent, but sometimes separated by enamel 

 wall into two (interior first, exterior afterward) lateral closed triangles. 

 Front lower with posterior spherical triangle; then interior closed triangle;, 

 then exterior closed triangle; then another internal closed triangle; then 

 the two next lateral angles (one on each side) not separated and closed by 

 a median enamel zigzag, but their dentine areas confluent, and moreover 

 running into the dentine island of the anterior trefoil — this trefoil of 

 variable shape. Thus there are five internal and four external angles in 

 all (counting the lobes of the anterior trefoil). Front upper molar with an 

 anterior spherical triangle, two interior and two exterior lateral closed 

 triangles, the last exterior one being postero-lateral. Second upper molar the 

 same, but with one less interior triangle — an exterior one comes first, then 

 the iuterior one, then the postero-external one : the latter does not develop 

 the postero-internal snag usually seen in Myonomes. Back upper with an 

 anterior spherical triangle ; then another like it reaching quite across the tooth, 

 but with its posterior median angle long and acute, and running into the 

 concavity of the posterior U, V, or Y that finishes the tooth. However this 

 last may vary in details, it never approaches the oblique crescent charac- 

 teristic of Myonomes. 



We only know one North American species of this section ; a second, 

 however, occurs in Mexico. 



ARVICOLA (PITYMYS) PINETORUM (LeConte). 



Pine Mouse. 



Arvicola pennsylvatuca, Harlan, Fn. Anier. 1825, 144 (in part; the description," but not the synonymy. 

 Kot of authors). 



Psammomys pinetorum, LeConte, Ann. Lye. Nat. Hist. N. Y. iii, 1829, 132, pi. ii. (Name inept.) 



Pilymys pinetorum, McMurtrie, Am. ed. Cnv. R. A. i, 1831, 434. 



Pincmys pinetorum, Lesson, Nouv. Tab. R. A. 1842, 12. 



Arvicola pinetorum, Aud. & Bach., Q. N. A. ii, 1851, 216, pi. lxxx (excl. syn. " oneida DeK.").— LeContk, 

 Proc. Acad. Nat. Sci. Philn. vi, 1853, 409. 



Arvicola (Pitymys) pinetorum, Baird, M. N. A. 1857, 544.— Allen, Bull. Mus. Comp. Zool. i, No. 8, 234 

 (Massachusetts ; rare; "probably its northern limit").— Allen, op. cit., ii, No. 3, 184 (Flor- 

 ida).— COOES, Proc. Acad. Nat. Sci. Phila. 1874, 191. 



Arvicola scalopsoides, Aud. & Bach., Journ. Acad. Nat. Sci. Phila. viii, 1842, 299 (Long Island).— Wagner, 

 Wiegmann's Archiv, 1843, 53.— LeConte, Proc. Acad. Nat. Sci. Phila. vi, 1853, 409. 



Arvicola apella, LeConte, Proc. Acad. Nat. Sci. Phila. vi, 1853, 405 (Pennsylvania).— AUD. & Bach., Q. N. 

 A. iii, 1854, 289. (Same as LeConte'*. ) 

 •"Above a brownish fawn; beneath grayish-white; * * length 4 inches; tail f of an inch; 



* * the teats of the female are situated very near the organs of generation ; she carries her young 



between the hind legs."— Harlan, I. c. 



