Igg PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



veloped. The length from the snout to the occipital condyle is 33 

 mm. The width at the articulation of the lower jaw is 23 mm. ; at 

 the base of the postorbital arch, 22 mm. The width of the inter- 

 orbital space, at the fronto-prefrontal suture, is 9.5 mm. The orbit 

 has a diameter of 10 mm., while the distance of the postorbital arch 

 from the rim of the auditory chamber is only 0.5 mm. The opening 

 of the auditory chamber is 5 mm. The distance from the tip of the 

 lower jaw to a line joining the hinder ends of the rami is 20 mm.; 

 from this line to the hinder end of the symphysis, 18 mm. 



This species appears to be most closely related to T . ornata, a spe- 

 cies now occupying Kansas and the regions to the southwest. It dif- 

 fers, however, in having the carapace narrower, or, at most, not wider, 

 across the eighth peripherals than near the transverse hinge-line. 

 Indeed, it seems to differ from all the living species in the same re- 

 spect. In most specimens of T. ornata there is a low ridge along the 

 midline and on each side of it a depression, features missing in 

 T. longinsulcB. The rami of the lower jaw of the fossil species are 

 nearly parallel as far forward as the coronoid process, whereas, in 

 T . ornata and T. Carolina they converge very perceptibly. The total 

 absence of a median carina distinguishes the fossil from T. Carolina. 



ASPIDERETES GRANIFER. new species. 



Plate XXVII. figs. 4, 5. 



In the U. S. National Museum there is one nearly complete costal 

 bone and some fragments of other costals of a trionychid turtle which 

 appears to be hitherto undescribed. This material was collected by 

 the late John B. Hatcher, July 10, 1887, at Cow Island. Montana. 

 The deposits here belong to the Judith Eiver Cretaceous. The speci- 

 men is Cat. No. 573G, U.S.N.M. 



The costal to be described is 199 mm. long. The width near the 

 neural border (fig. 5) is 40 mm.; at the free border (fig. 4), 62 mm. 

 The thickness where it joined the neural is 4 mm. ; near the free 

 border, i> mm. The free border is cut off at nearly a right angle with 

 the upper surface, but the upper layer of the bone does not overhang 

 the deeper layers. The rib did not extend beyond the free border 

 of the disk, an indication of the great age of the animal. The disk 

 must have been somewhat more than 400 mm. wide. 



It is the character of the sculpture of the upper surface that dis- 

 tinguishes this turtle from all others yet known. The general 

 appearance is that of a network of narrow, smooth, and sharply 

 defined ridges surrounding flat-bottomed pits. Of these pits there 

 are 4 in a line 10 mm. long. At the proximal end of the bone (fig. 

 5) the bottoms of the pits are shagreened ; and in some of them there 

 is a little elevation that resembles a glass bead or a grain of sand. 



