Fig. 
Fig. 
Fig. 
All 
EXPLANATION OF THE PLATES. 
. 8—Hespéeromys boylii, Baird.—No. 127 0.—Middle fork of American river, Cal.... 
References a—-g, as in fig. 1; fand g magnified nearly three diameters. 
. 4 Hesperomys (Oryzomys) palustris, — & —No. 2111.—Society Hall, 8, C........... 
References a—g, as in fig. 1. 
ge. 5—Hesperomys texanus, Woodh.—No. 2217.—Turkey creek, Texas..........-.+++++++ 
Grinding surfaces only of the molar teeth ; a—of left upper molars ; b—of 
left lower molars, magnified rather more than twice. 
. 6—Mus tectorum, Savi.—White-bellied rat.—No. 1685.—Cadcreita, New Leon... 
References a-g, as in fig. 1; f and g magnified twice. 
PLATE LIII. 
1—Neotoma fuscipes, Cooper.—Bush rat.—No. 2040.—Santa Clara, California... 
Male quite old. a—skull from below ; )—skull from above; c—skull from 
the side; d—left side of lower jaw ; e—left side of lower jaw from above; 
jf—upper molars of left side ; g—lower molars of left side. The two last 
magnified three times. 
2—Neotoma floridana, Say & Ord.—Wood rat.—No. 2056.—St. Simon’s island, 
GeOrpiaiceecten custome coast onakescke set tascsnessrscehoncssacsensmrsshscssnnnsscice 
Very large and old. References a-g, as in the last. Two last magnified 
three times. 
3—Neotoma occidentalis, Cooper.—Brush-tailed rat.—No. 1591.—Shoalwater bay, 
Washington Morritory se qeses- cote. o- cease a- comes tot snise ces tease acre eeanes -seneenaer 
Not very old. References a-g as in fig. 1; f and g magnified twice. 
. 4— Neotoma magister, Baird.—Fossil ; from the bone cave at Carlisle, Pa.......... 
a—left side of lower jaw; b—left side of lower jaw from above. 
. 5—Neotoma cinerea.—Rocky Mountain rat.—No. 2159.—Fort Sarpy? Yellow- 
Stone Trivers Nebraskar....cassea-tecseteees cas chnccactes ovarettcdsocesssxecacsseussees 
References a—-g as in fig. 1; f and g magnified rather more than twice. 
. 6—Sigmodon berlandieri, Baird.—Texas cotton rat.—No. 1672.—West of San 
ANTONIO... cave cccascuseee eh <catecbsehesaskt ener ne :cremonenshs criennanmecanenrancanstoas 
Very old. References a—g as in fig. 1; fand g magnified rather more than 
three times. 
. 1—Sigmodon berlandieri, Baird.—No. 1681.—Santa Rosalia, Mexico....... sss. 
Rather young. a—grinding surface of left upper molars; b—grinding 
surface of left lower molars. Magnified nearly three times. 
PLATE LIV. 
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. 
. 1719—Arvicola pinetorum, Lec.—No. 45’? .—Georgia.........sccecsenersesececeeseceseees 
. 1714—Arvicola cinnamomea, Bd.—No. 
. 2211—Neotoma mexicana, Bd.—No. 2344.—San Pedro river, Somora......s.cseeeeeees 
$96 
i o . Pemibin asin. cedeietedes eee ne 
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