288 
TERTIARY VERTEBRATA OF THE FAYtM. 
it is at once distinguished by the circumstance that the o])isthotic and the squamosal 
join as usual, and there is a distinct epipterygoid, indicating that this Turtle is a 
member of the Chelonidm. The occipital condyle is trilobate and the basioccipital 
portion thrusts itself betvTeen the exoccipital lobes, reaching the foramen magnum. 
In front of the occipital condyle the ventral face of the basioccipital is compara- 
tively flat, and there is no deep depression at its union with the basisphenoid as in 
Chelone\ laterally, together with the exoccipitals, the basioccipital forms a flat vertical 
surface, whicli is larger than is found in either Chelone or Thalassochclys. The 
oj)isthotics (o.o.) are arranged as in the recent types and are firmly united at 
their outer ends with the squamosals {sq.) ; they form the upper border of a large 
fossa into which several foramina opened. The form of the tympanic cavity {t.o.) 
is almost as in Chelone ; it seems, however, to be a little more sharply defined 
in front and a little more elongated in a vertical direction. The pedicle of the 
quadrate [q.) is longer than in the recent forms, so that the articular surface for 
the mandible is further below the level of tlie palate. 
The basisphenoid bears a pair of ridges, which converge forwards meeting in the 
middle line ; on its upper (cranial) surface there is a strong median ridge. The 
epipterygoids arise by a narrow base and are less flattened from within outwards than 
in Chelone or Thalassochelys caretta. 
There is no doubt that the skull here described is that of a member of the 
Chelonidm, and since in the form of its basioccipital and basisphenoid it resembles 
the skull of Thalassochelys rather than that of Chelone, it is referred to that genus ; 
but further material in better preservation is required before its precise position can 
be made out. 
C. 10029. Posterior portion of skull, uncrusbed but niucb covered witb a reddish matrix and 
apparently impregnated with salt. Tbe type described in Geol. jMag. [4] vol. viii. p. 441. 
Figured PI. XXV. fig. 4. Tbe dimensions (in centimetres) of tins speeinam are: — 
Height of skull (from basisphenoid to roof) 7’5 
(freatest width at squamosals loH 
Width between outer angles of tbe quadrates 1245 
„ of occipital condyle 2'4 
C. 10030. Much crushed and weathered skull, incomplete in front, showing tbe roofed-in temporal 
fossse. 
R. 3192. A similar but rather more im[)erfect specimen. 
PresenLcd luf ihe hhri//>tian Covernme/it, 1904. 
