No. 1.] RELATIONSHIPS OF PROTOSTEGA. 27 
deep groove running forward and upward which receives the 
epipterygoid process from the quadrate. 
The posterior half is not perforated by a branch of the car- 
otid artery as in the Chelonitdae, nor does any foramen for this 
artery appear on the back of the skull as in that family. In 
these points of difference from the Cheloniidae, and in the fact 
previously mentioned that it is separated from the exoccipitals 
by the lateral processes of the basioccipital, the pterygoid 
agrees with Dermochelys (Pl. V, Fig. 6). 
The falatines are present in an imperfect condition. The 
anterior and interior portions are gone, and the whole bone is 
distorted by pressure; enough remains, however, to show that 
there were deep choanae located far forwards which were not 
roofed by the vomer and palatines. This condition of the 
internal nares is largely that of Dermochelys, in which the 
choanae are far forward, and are not roofed by the palatines and 
vomer. The articulation with the maxillaries was by a deep, 
elongated, triangular region, as in the typical Cheloniidae (EL 
V, Fig. 6). 
The vomer is present in a fragmentary condition. It did 
not have a process descending between the palatines, and help- 
ing to roof the choanae, as in the Cheloniidae. 
The guadratojugal of the right side is triangular in general 
outline. The posterior edge is concave, and the whole bone is 
convex from above downwards. The superior edge is narrow, 
and there is no prolongation of the antero-inferior portion, as 
in Dermochelys (Pl. V, Fig. 7). 
The sguamosal of the right side shows a broad concave sur- 
face for the upper end of the quadrate. The posterior inferior 
portion shows no groove as in the Cheloniidae. The anterior 
portion is thin and expanded. 
The mandible is present in a singularly perfect condition, 
the only parts injured being the posterior portions of the com- 
plementaries. It is figured in Pl. V, Fig. 8. The whole jaw 
resembles very much that of the Cheloniidae. 
The dentary is broad from above downwards, with the upper 
surface slightly concave in the region of the symphysis, and 
marked by deep pits. The symphysis is broadly triangular, it 
