288 TEETIAET VEETEBRATA OE THE FATtTM. 



it is at once distinguished by the circumstance that the opisthotic and the squamosal 

 join as usual, and there is a distinct epipterygoid, indicating that this Turtle is a 

 member of the Chelonidse. The occipital condyle is trilobate and the basioccipital 

 portion thrusts itself between 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, which is larger than is found in either Chelone or Thalassochelys. The 

 opisthotics {o.o.) are arranged as in the recent types and are firmly united at 

 their outer ends with the squamosals {sg^.) ; 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 the 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 

 Chelonidse, 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, uncrushed but much covered with a reddish matrix and 

 apparently impregnated with salt. The type described in Geol. Mag. [4] vol. viii. p. 441. 

 Figured PI. XXV. fig. 4. The dimensions (in centimetres) of this specimen are : — 



Height of skull (from basisphenoid to roof) 7"5 



Greatest width at squamosals 15'4 



Width between outer angles of the quadrates 12'3 



„ of occipital condyle 2'4 



C. 10030. Much crushed and weathered skull, incomplete in front, showing the roofed-in temporal 

 fossae. 



R. 3192. A similar but rather more imperfect specimen. 



Presented hy the Egyptian Government, 1904. 



