ii8 AMERICAN MESOZOIC MAMMALIA 



Of the older figures, the following are of specimens now referred to Pediomys: 



Marsh 1889A, PI. IV, figs. 23-25. 



1892A, PI. IX, fig. I. 

 PI. X, fig. 3. 

 Osborni893, PI. VIII, A, B. 



1898, fig. I, A. 



Pediomys elegans Marsh 1889 

 1889. P. elegans, Marsh, Amer. Jour. Set. (3) XXXVIII, 89. 



Type. — Y.P.M. No. 11866. Isolated upper molar, broken and weathered. Fig'd, 

 Marsh 1889A, PI. IV, figs. 23-25. 



Neotype. — Carnegie Mus. No. 11658. Upper jaw with M^*. Fig'd, Simpson 

 1929B, fig. 3. 



Horizon and Locality. — Lance formation, Niobrara County, Wyoming. Re- 

 ferred specimens from Dawson County, Montana. 



Diagnosis. — Not precisely definable. Used in a broad sense for the smaller forms 

 of Pediomys from the Lance and its equivalents. 



Several species are clearly represented in the material referred to P. elegans. The 

 known characters of the genus as a whole are given below, under P. hatcheri. 



Pediomys hatcheri (Osborn 1898) 

 1898. Protolambda hatcheri, Osborn, Bui. Amer. Mus. Nat. Hist., X, 172. 



Syntypes. — Amer. Mus. Nos. 2201, 2202, 2203.^* Isolated right upper molars. 

 Fig'd, Osborn 1898, fig. i, A. 



Horizon and Locality. — Lance, Niobrara County, Wyoming. 



Diagnosis. — Not exactly definable. Used in a broad sense for the larger forms of 

 Pediomys from the Lance and its equivalents. 



Under this head all of the teeth definitely referable to the genus may be described. 



Dentition 



The genoholotype, Y.P.M. No. 11 866, is very badly preserved, although suffi- 

 ciently clear to validate the genus. Y.P.M. No. 10682 (Fig'd, Marsh 1892 a, PI. X, 

 fig. 3) is closely similar and better preserved. It is apparently a second or third upper 

 molar of the right side. The crown consists essentially of a nearly symmetrical trigon. 

 The protocone is stout, relatively blunt, subcrescentic, without anterior or posterior 

 basal cingula. On the external slope of the pr are the two conules, which are small, 

 crescentic, and of about equal size. The anterior ridge of the paraconule continues 

 externally at the level of the crown and rises into the anterior stylar cusp, A (below), 

 while the corresponding posterior crest of the metaconule runs outward and upward 

 toward the base of the tooth and then disappears. The median ridges of the two conules 



^° Osborn states that the types are four molars, but he only designates and figures these three. 



