748 
EXPLANATION OF THE PLATES. 
Page. 
Fig. 3— Eesperomys boylii, Baird.—No. 1270.—Middle fork of American river. Cal.... 471 
References a-g, as in fig. 1; /and g magnified nearly three diameters. 
Fig. 4— Eesperomys (Oryzomys) palustris. — 6 —No. 2111.—Society Hall, S. C...... 482 
References a-g, as in fig. 1. 
Fig. 5— Eesperomys texanus, Woodh.—No. 2217.—Turkey creek, Texas. 464 
Grinding surfaces only of the molar teeth ; a —of left upper molars ; b —of 
left lower molars, magnified rather more than twice. 
Fig. 6— Mus tectorum, Savi.—White-bellied rat.—No.-1685.—Cadcreita, New Leon.... 441 
References a-g, as in fig. 1; / and g magnified twice. 
PLATE LIII. 
Fig. 1— Neotomafuscipes , Cooper.—Bush rat.—No. 2040.—Santa Clara, California.... 496 
Male quite old. a —skull from below ; b —skull from above; c —skull from 
the side ; d —left side of lower jaw ; e —left side of lower jaw from above; 
/—upper molars of left side ; g —lower molars of left side. The two last 
magnified three times. 
Fig. 2— Neotoma floridana, Say & Ord.—Wood rat.—No. 2056.—St. Simon’s island, 
Georgia. 487 
Very large and old. References a-g, as in the last. Two last magnified 
three times. 
Fig. 3— Neotoma occidentalis, Cooper.—Brush-tailed rat.—No. 1591.—Shoalwater hay, 
Washington Territory. 496 
Not very old. References a-g as in fig. 1; / and g magnified twice. 
Fig. 4— Neotoma magister, Baird.—Fossil; from the hone cave at Carlisle, Pa.. 498 
a —left side of lower jaw ; b —left side of lower jaw from above. 
Fig. 5— Neotoma cinerea. —Rocky Mountain rat.—No. 2159.—Fort Sarpy? Yellow¬ 
stone river, Nebraska. 499 
References a-g as in fig. 1; / and g magnified rather more than twice. 
Fig. 6— Sigmodon berlandieri, Baird.—Texas cotton rat.—No. 1672.—West of San 
Antonio. 504 
Very old. References a-g as in fig. 1; / and g magnified rather more than 
three times. 
Fig. 7— Sigmodon berlandieri, Baird.—No. 1681.—Santa Rosalia, Mexico.. 504 
Rather young, a —grinding surface of left upper molars ; b —grinding 
surface of left lower molars. Magnified nearly three times. 
PLATE LIY. 
All the figures in the present plate represent the grinding surfaces of the molar teeth 
on the left side of the jaw. The one above the number belongs to the 
superior molars, the lower figure to the inferior ones. 
No. 1719— Arvicolapinetorum, Lee.—No. V/e 9 .—Georgia. 544 
No. 1714— Arvicola cinnamomea, Bd.—No. Vv 1 /•—$ . Pembina... 541 
No. 2211— Neotoma mexicana, Bd.—No. —San Pedro river, Sonora.. 490 
