826 THE WHITE RIVER FAUNA. 



Gymnoptychus trilophus Cope. 



Paleontological Bulletin No. 16, p. 6 (August 20, 1873). Annual Report U. S. Geol. Surv. Terrs., 1873 



(1S74), p. 476. 



Plate LXV; figs. 31-34. 



This squirrel is represented by mandibles only of a small number of 

 individuals, although very similar to the species last described in most 

 details it is constantly of larger size, and I have seen no individual pro- 

 portioned so as to be intermediate between them. 



Three of the inferior molars of this species have the same longitudinal 

 extent as the four, or entire series of the G. minutus. The detailed struct- 

 ure of the molars is the same as in that species. Attrition very soon causes 

 the union of the exterior cross-crests with those which proceed from the 

 cusps, producing as a result only three transverse yokes, and a figure some- 

 thing like the Greek ay. The delicate groove of the inferior incisor, and 

 the posterior protuberance of its sheath, are as in G. minutus; so also the form 

 of the masseteric fossa, the position of the mental foramen, etc. The pre- 

 molar is relatively a little more elongate than in the G. minutus, but its 

 details are the same. The diastema is relatively shorter. 



Measurements. 



M. 



Length of inferior molar series 0065 



Length of inferior diastema .0045 



Depth of inner face of ramus iit diastema 0035 



Depth of inner face of ramus at first molar 0040 



Depth of inner face of ramus at last molar 0035 



Depth of inner face of ramus at coronoid process 0052 



Diameter of inferior incisor ^■'"'•""Ol'o^t^"'"" ^^^ 



I transverse 0010 



Diameter of second molar ^^"*'''""P''«'"'°'' ""^^ 



( transverse 0015 



I discovered this species in the same locality as the G. minutus. 



MENISCOMYS Cope. 



Paleontological Bulletin No. 30, p. 5, December 3, 1878. Proceed. Amer. Philos. Soc, 1878 (1879), p. 67. 



The characters of this genus are derived from the dentition of both 

 jaws, and from portions of the cranium which are preserved. The molars 

 are rooted, and number f or f f. Those of the superior series are 

 without enamel inflections, and the triturating surface exhibits two external 



