INO T.(] RELATIONSHIPS OF PROTOSTEGA. 37, 
so that they touched for a great part of their length. The 
process bearing the articular faces for the other bones of the 
pelvis is short and strong (Pl. VI, Fig. 15). 
MEASUREMENTS. 
Length from proximal end to end of ectopubis . . . . . . .243 meters 
se “« external edge of bone to ischial symphysis . . . .169 “ 
a “« point on shaft opposite center of entoischium to 
proximal end sea fs 1m oak eS ey OST 
The zschtwm is somewhat hourglass-shaped in profile, with 
the distal end the largest and the middle of the bone much con- 
tracted. The broader portion of the shaft is thin, and the 
anterior edge rounded and thickened. The symphysial edge 
is somewhat convex, the two bones meeting probably in the 
middle portion only. The pubo-ischiatic foramen was small in 
Dermochelys (Pl. VI, Fig. 16). 
The z/ium is a short, strong bone, concave on its lower sur- 
face, and angularly convex above from before backwards. The 
distal articular surface is confined to the end of the bone. The 
center of the upper side is rugose for cartilaginous attachment 
(Pl. VI, Fig. 17). The figure of the ilium is made from the 
smaller specimen, as it is much more perfect than the larger. 
The femur is much smaller and more slender than the 
humerus. The distal end is expanded. The shaft is contracted 
below the head, which was supported on a well-developed neck 
(El Way. Figs 18). 
MEASUREMENTS. 
Renpthortemur. 2) ek be is a |; . .295 meters 
Greatestibreadthadistalyendijy sian en ne eo ne 
Breadth center of shakes iii. a). io 4 +.) 2098) Y“ 
Protostega has, then, the following points in common with 
the Cheloniidae: the peripherals, the condition of the plastron 
(part.), the lack of such a large amount of intercalated cartilage 
in the articulations of the bones of the skull, the nature of the 
semicircular canals in the paroccipital, petrosal, and exoccipital, 
and the shape of these bones; the formation of the foramen for 
the external carotid by the petrosal and quadrate to the almost 
complete exclusion of the paroccipital, the form and position of 
