Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 29 
sphenoid in this specimen. ‘There is, however, a slight projection in 
the middle of the opening behind, which may represent a more 
extensive ossification, but it seems very probable that there was a 
real vacuity here, unlike the condition in Pe/oneustes and Plesiosaurus. 
The union with the vomer is oblique, from without inward and 
forward. 
The palatine and ectopterygoid on one side, though retaining 

pw 
pt 
N \ 
AB bs 
cn i 
\ Hy 
FIG. 1. FIG 72, 
Palate of Peloneustes. Palate of Plestosauris. 
Px., premaxilla; wx., maxilla; v., vomer; z., internal nares; fa., palatine; f7., pterygoid; 
fv., posterior palatine vacuity; ¢ef., ectopterygoid; és., basisphenoid; 40., basioccipital; g., quad- 
rate; sg.,squamosal. After Andrews. 
their original positions approximately, were free in the specimen; 
they are complete and show their sutural relations very well. On the 
other side, they are both in position. The palatine is a long, narrow, 
thin bone, concave from side to side above, and correspondingly con- 
vex below. The inner, slightly sinuous margin is thin, and overlaps 
the outer margin of the palatine process of the pterygoid. Near its 
anterior extremity there is a small emargination for the nares*, where 
*See description of the palate in Brachauchenius beyond. 
