194 FOSSIL TURTLES OF NORTH AMERICA. 



Millimeters. 



Extreme length of ramus of lower jaw 370 



Extreme length of symphysis of lower jaw 1 60 



Length of skull from beak to end of supraoccipital spine 580 



Median length of narial opening 75 



Width of narial opening 55 



Antero-posterior length of orbit 120 



It will be observed that this skull was nearly 2 feet in length. In Wieland's figure the 

 suture between the parietals was omitted; but this is here supplied. 



It is unfortunate that only a portion of the nuchal was preserved. Its presence would have 

 settled the question regarding the identity of the T-shaped bone, which has been regarded as 

 the nuchal. The portion of the nuchal (fig. 248, nu. p) remaining with this specimen does not, 

 the writer believes, particularly favor the opinion that it is the T-shaped bone. 



No. 1393 of the Carnegie Museum was obtained at Twin Butte Creek, Logan County, 

 Kansas. It is fragmentary, but presents various portions of the plastron, limbs, and skull. 



FIG. 249. Protostega gigas. X i'. Carapace of No. 1420 Carnegie Museum. 

 I 10, the ribs of the carapace; s, sacral rib. 



Some series of the peripherals show that there was a sharp free border along each side. From 

 this a plate of bone from 50 to 70 mm. wide rose over the distal ends of the ribs. From the 

 same border another plate, from 25 mm. to 30 mm. wide, past horizontally inward below the 

 rib-ends. The hyoplastron and the hypoplastron taken together measure about 400 mm. in 

 length. The greatest thickness of the hyoplastron is about 15 mm. The hypoplastron is 

 somewhat thinner. Both xiphiplastra are present. They are of the form shown in Case's 

 figure, but they are not so abruptly bent. 



Little is known regarding the vertebrae of this species. Cope had remains of 5, but he was 

 unable to determine where they belonged. They probably appertained to the tail. Cope 

 supposed that the dorsal vertebrae possest transverse processes, but Wieland's figure shows 

 this conclusion to have been erroneous. Wieland stated that a specimen at the Carnegie 

 Museum furnisht 6 of the cervicals, but he did not describe them. Case describes 2 caudals. 

 They were procoelous. 



The carapace of this species is of great interest, and has been studied by Cope, Case, and 

 Wieland. Cope had secured portions of 10 ribs of the type specimen. He recognized clearly 



