38 CASE. [VoL. XIV. 
the quadrate, the form of the squamosal and its close articula- 
tion with the quadrate, the articulation of the paroccipital with 
the squamosal, the well-ossified and separated condylar portions 
of the exoccipital and basioccipital, the manner of articulation 
of the palatines with the maxillaries, the posterior nares (part.), 
and the form of the mandible. 
With Dermochelys it agrees in, the broad basioccipital with 
its lateral processes preventing the articulation of the pterygoid 
and exoccipital, the broad basisphenoid separating the ptery- 
goids on the base of the skull (to a less extent than in Dermo- 
chelys), the nonappearance of the pterygoids on the posterior 
aspect of the skull and their not being perforated by a branch 
of the carotid artery, the large groove on the pterygoid for the 
epipterygoid process of the quadrate, the large epipterygoid 
process of the quadrate, the posterior nares (part.), and the 
vomer, the lack of a carapace, the large nuchal, the humerus 
(part.), and the plastron (part.). There should also be mentioned 
here the stapes, which is even larger than in Dermochelys. 
Points separating Pvotostega from both forms are the lack of 
dermal ossifications on the back, the manner of articulation of 
the pterygoid and quadrate, the presence of a presplenial bone 
in the jaw, the lack of any articular process on the under side 
of the nuchal, the simple radial process of the humerus, and 
the peculiar bent form of the xiphiplastra. 
Protostega is distinctly an intermediate form. 
In the paper containing the description of Pyvotostega (2) 
Cope attempted a restoration from the material at his command. 
He estimated the head as 243 inches long, and by assuming 
the proportions to be near those of Chelonza, the neck and cara- 
pace as 1382 inches, making a total length of 154% inches, or 
12.83 feet. (He evidently deducted 8 inches from the neck as 
remaining within the carapace.) From the ribs and vertebrae 
he estimated the width of the carapace to be 36} inches, and 
the length 118 inches. The series of marginals did not justify 
this length, but he considered that they were not united, and 
that the intervening spaces would make up the deficiency. His 
final conclusion was that the carapace was more elongate and 
narrower than in any existing form of sea turtle. 
