95 



That genus has so far only been found in the Eocene formation. The bone 

 is rather thin, and sufficiently curved to indicate a convex carapace of moder- 

 ate thickness. The surface is marked with closely-packed shallow pits with- 

 out material variation of form on the proximal half of the bone. The result 

 is an obsolete sculpture quite similar to that seen in some species of the 

 genus to which it is at present referred. 



Measurements. 



M. 



Width of the costal bone 0. 0230 



Thickness of the costal bone 0. 0033 



Number of pits in m .010, G. 



Lignite Cretaceous of Colorado ; also, sevei'al fragments from Long 

 Lake, " Nebraska,'' from Dr. Hayden. 



1 Plastomenus insignis, sp. nov. 



Represented by a portion of the right hyposternal bone of a tortoise 

 about the size of the last species, and from the same locality. The specimen 

 resembles, in its sculpture, such species as the Plastomenus trionychoides, and, 

 in structural character, the species of Anostira, but it is scarcely probable that 

 it belongs to either genus. It is flat, and has a narrowed, straight, inguinal 

 margin, at right angles to the fine suture with the hyosternal. The suture 

 with the postabdominal is partially gomphosial. Surface dense, polished, 

 marked externally with a reticulate sculpture of narrow ridges separating 

 larger and smaller areas wider than themselves. Inguinal edge thinner. 



Measurements. 



M. 



Length of the hyposternal fore and aft 0. 025 



Thickness of the hyposternal at front 0. 004 



Pits in m .010, sis. 



Lignite Cretaceous of Colorado. 



TEIONYX, Geoffr 



Although species of this genus occur in the greensand of Cretaceous No. 

 4, in New Jersey, none have been discovered in the West below the horizon 

 of No. 6, or the Fort Union fresh-water beds. Dr. Leidy has described a T., 

 foveatus from the bad lands of the Judith River, Montana ; and I have added 

 the following: 



