OSTEOLOGY. 0) 
The skull of the Cheloniidz differs in some important respects from that of the 
Emydidz. In order to illustrate this, figures are here introduced giving upper 
(plate 1, fig. 1), lower (plate 1, fig. 2), and lateral (plate 2, fig. 1) views of the skull 
of Lepidochelys kempi Garman. These figures were prepared for Dr. George Baur, 
in 1888, but reverted to the United States Geological Survey, the then director of 
which, Dr. C. D. Walcott, has permitted them to be used here. No figures of 
this species have hitherto been publisht. he most interesting feature of the 
skulls of the sea-turtles is the great extent of the bony roof covering the temporal 
region. This roof extends from the orbit to behind the plane of the occipital con- 
dyle. The postfrontal bone, narrow in the emyds, is carried backward nearly to 
the hinder border of the roof. he squamosal sends upward and inward a plate 
that meets a horizontal plate from the parietal, forming a parieto-squamosal arch. 
‘The lower side of the skull is interesting 
chiefly because of the broadening of the triturat- 
ing surfaces of the jaws. The palatal plates of 
the vomer extend backward until they meet 
similar plates from the palatines. The choane 
are thus thrown much farther toward the middle 
of the skull than in the skull represented by text- 
figure 4. The crushing surfaces of the lower 
jaw are correspondingly widened (plate 1, figs. 
3 and 4). In the Thalassemydide the choane 
may be pusht much further backward, as ma 
be seen by examining the skull of Rhetechelys 
platyops (Cope). There are no posterior palatine foramina. 
In the Cheloniidz the procoracoid process makes an obtuse angle with the body 
of the scapula, and there is a distinct neck between the process and the glenoid 
fossa. The coracoid bone is longer than the scapula and moderately expanded at 
its free end. hese bones are represented by fig. 2 of plate 2. 
The humerus of these sea-turtles is strongly modified from the primitive form. 
It is much straighter than that of the Emydide and has become flattened in the 
plane of the distal end. ‘The head and the radial and ulnar tuberosities have changed 
positions. The head is turned downward and proximad into the plane of the bone, 
while the tuberosities are lifted into this plane, each on its proper border of the bone. 
The radial tuberosity is carried along on the shaft of the bone until it has lost its 
connection with the head. It becomes divided into two parts, one for the deltoid 
muscle, the other for the supracoracoid. Fig. 3, plate 2, represents the humerus of 
Lepidochelys as seen from above; fig. 4, as seen from below. 
Relatively to the humerus, the radius and the ulna are shortened, the ulna 
more than the radius. In the carpus the radiale remains small, the intermedium 
and the ulnare are enlarged and flattened, while the centrale is distinct. There are 
five bones in the distal row, one articulating with each metacarpal. The third and 
the fourth may be co-ossified. On the ulnar side of the carpus there is a large flat 
bone assisting to broaden the carpus. It may be regarded as the pisiform. 
The second, third, and fourth digits are greatly elongated, the bones flat- 
tened, and all are bound together in a mass of muscles and skin to form an undivided 
oar. The first, and in some cases the second, digit is provided with a claw. 
The pelvis of the Cheloniidz is broad and deprest (fig. 5). The ilia are short; 
the upper end is slender and turned backward and the axis of the bone is nearly 
in the plane of the pubes. The latter bones are broad. Between the two, at the 
Fic. 5.—Caretta caretta. Pelvis from 
below. x. 
