748 EXPLANATION OF THE PLATES. 



Page. 



Fig. 3 Hesperomys 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 Hesperomys (Oryzomys) palustris. 6 No. 2111. Society Hall, S. C 482 



References a-g, as in fig. 1. 

 Fig. 5 Hesperomys texanus, Woodh. No. 221*7. 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 tectontm, 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 Neotoma fuscipes, 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 bay, 



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 bone 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 LIV. 



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 Arvicola pinetorum, Lee. No. VVy. Georgia 544 



No. 1714 Arvicola cinnamomea, Bd. No. Wr 4 - $ . Pembina 541 



No. 2211 Neotoma mexicana, Bd. No. ^rH- San Pedro river, Sonora 490 



