300 PALAEONTOLOGY. 



for the prehension of fishes ; and their skeleton was modified 

 for more efficient progress in water by the vertebral surfaces 

 being slightly concave, by the hind limbs being relatively 

 larger and stronger, and by the orbits forming no prominent 

 obstruction to progress through water. From the nature of 

 the deposits containing the remains of the so-modified cro- 

 codiles, they were marine. The fossil crocodile from the 

 Whitby lias, described and figured in the Philosophical Trans- 

 actions, 1758, p. 688, is the type of these amphiccelian species. 

 They have been grouped under many generic heads: — e.g., 

 Teleosaurus, Steneosaurus, Mystriosaurus, Dakosaurus, Macro- 

 spondylus, Massospondylus, Pcecilopleurcm, Pelagosaurus, JEolo- 

 don, Suchosaurus, Goniopholis, etc., and they range from the 

 lias to the chalk inclusive. 



Suchosaurus of the Wealden is characterized by the com- 

 pressed crown and trenchant margins of the teeth ; Gonio- 

 pholis, of the Purbeck beds, by some of the dermal scales 

 having the same peg-and-pit interlocking as in the scales of 

 the ganoid fish in fig. 71. 



Sub-Order 2. — Opisthocoilia. 

 The small group of Crocodilia so called is an artificial one, 

 based upon more or less of the anterior trunk vertebrae being- 

 united by ball-and-socket joints, but having the ball in front, 

 instead of, as in modern crocodiles, behind. Cuvier first 

 pointed out this peculiarity* in a Crocodilian from the Ox- 

 fordian beds at Honfleur, and the Kimmeridgian at Havre. 

 The writer has described similar opisthocoelian vertebrae from 

 the great oolite at Chipping Norton, from the upper lias of 

 Whitby, and, but of much larger size, from the Wealden for- 

 mations of Sussex and the Isle of Wight. These specimens 

 probably belong to the fore part of the same vertebral column 

 as the middle dorsal vertebrae, flat at the fore part, and 



* Annales du Museum, torn, xii., p. 83, pis. x., xi. 



