194 FOSSIL TURTLES OF NORTH AMERICA. 
Millimeters. 
Extreme lengthiof-ramuss of lowertawcs <i csi ee eer eee 370 
Extreme length/ofsymphysis of lower jaws 2.1.0. 92) s cmt soa clase 160 
Length of skull from beak to end of supraoccipital spine................-- 580 
Median lengthof narial opening. 22)... oe eet oe ees Oy aA 75 
Width of narial opening........... Aa gs Ccpee tee eae 55 
Antero-posterior length of orbit........... Rt Ahi ras Seen ete Sea She 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 haye 
settled the question regarding the identity of the T-shaped bone, which has been regarded as 
the nuchal. The portion of fhe nuchal (hg. 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. 
Fic. 249.—Protostega gigas. 1's. 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. ‘he greatest thickness of the hyoplastron is aan 15 mm. The hypoplastron 4 is 
somewhat hinned 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 vertebra of this species. Cope had remains of 5, but he was 
unable to determine here ‘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 proccelous. 
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 
