182 THE WASATCn A^TD BRIDGER FAUN^. 



Plesiabctomys delicatior Leidy. 



Cop«, Report U. S. Geog. & Gool. Expl. Surv. W. of 100th M.r. G. M. Wheeler, iv, pt. ii, p. 172. Para- 

 myi deUcati<»r Leidy, Proceed. Acad. Phila. 1B71, p. 231. Report U. S. Geol. Surv. Terrs. ISTJ, 

 i, p. 110, pi. vi, Ugs. '2(>-7, pi. xxvii, tigs. 16-18. 



Plate xxiva, tigs. 11-13. 



This squirrel is represented by the jaws of at least four individuals in 

 Mr. Wortman's Wind River collections. Two of these are further repre- 

 sented by other portions of the skeleton, one of theiu including a maxillary 

 bone with four molars in place. 



The bones of the skeleton coincide with the teeth in their superior 

 dimensions as compared with those of the P. delicatissimm. The pieces of 

 the last-named individual which are preserved are portions of the femur 

 and tibia, with astrogali and calcanea ; also, portions of ulna and metatar- 

 sals and ribs. The only difference of form I observe between these and 

 corresponding parts of P. delicatissimus is in the distal extremity of the tibia ; 

 This has a relatively greater transverse diameter as compai-ed with the 

 anteroposterior than in the species just named. The calcaneum of the 

 right side is nearly perfect. The free portion is strongly compressed ; the 

 anterior portion appears depressed on account of the extent of the sustenta- 

 culum on the inner side, and the well-developed corresponding process on 

 the external side opposite to it. The cuboid facet is, however, as deep as 

 wide, and truncates the calcaneum transversely. The external astragaline 

 facet is very convex, and presents inwards and a little forwards. 



The superior molars accompanying, this specimen are of the size and 

 proportions of the inferior molars, but they belong to the Mesodont, Pehj- 

 codus frugivorus, described later in the present work, where the distinction 

 between the molar teeth of this genus and those of Pelycodus are pointed out. 



Measurements. 



M. 



Length of inferior molar series 016 



Length of last inferior molar 005 



Longlh of diastema 0085 



Depth of ramus at ponultimute molar 0115 



Diameter of shaft of tibia two-fifths distance from extremity 0073 



„. ^ /■ • • r .t ■ (anteroposterior 0095 



Diameters of extremity of tibia? 



\ f riinsverse 01 10 



antemposterior 009O 



Diameters of trochlea of astragalus \ 



traasverbo OOSO 



