636 BRITISH FOSSIL REPTILES. 



Portions of dermal scutes, with the pitting as on the mandible, but with wider intervals, 

 are preserved on the slab in which the above-described fossil is imbedded. 



A few Wealden vertebrae, not associated with characteristic parts of any of the fore- 

 going (pp. 431, 631, 634) CrococUlia, differ from those in Plate 10 by the carinate 

 under surface of the centrum. They are figured in CrocodUia, Plate 14, under the 

 provisional name of Goniopholis carinatus. 



Of the known species of mesozoic Crocodiles, including the Purbeck and Wealden 

 kinds now added, the following are common characters. A greater development, than 

 in Tertiary Crocodiles, of the dermal bony armour, which consists, without exception, of 

 both dorsal and ventral scutes, the scutes in each series well connected with each other, 

 and in Goniopholis exceptionally so. A less development of the osseous surface for the 

 origin of the muscles of the mandible indicated at the upper surface of the cranium by 

 the larger ' temporal vacuities,' and at the under surface by the smaller pterygoid plates. 

 The horizontal plane, larger size, advanced position and palato-pterygoid formation of the 

 palatonares. Relatively small fore-limbs ; Amphicoelian vertebrae in most, in none 

 Proccelian. 



These common characters of mesozoic CrocodUia suggest considerations of their 

 relation to the prey of such CrocodUia and also to the coexistent marine reptiles of which 

 those CrocodUia themselves became the prey. 



Similarly, if the common characters of the tertiary and existing CrocodUia be 

 summed up they become suggestive of analogous considerations. They are : — cup-and-ball 

 vertebrae, the cup in front ; fewer dermal scutes, not co-articulated suturally or by peg- 

 and-socket joints ; posterior aspect and position of small and exclusively pterygoid 

 ' palatonares ;' upper temporal apertures, when present, less than the orbits; fore-limbs 

 relatively larger than in Amphicoelians ; with one exception jaws stronger with larger and 

 more varied teeth. 



The Proccelian articulation of the trunk-vertebrae better adapts that part of the body 

 to be sustained and moved in air than the Amphicoelian articulation which characterises 

 the vertebral column of the more aquatic and probably marine Crocodiles of the Mesozoic 

 period. 



The presence of prey not in existence at those periods, but which in later, tertiary 

 and modern times, might tempt a Crocodile to rush on shore in pursuit of a Mammalian 

 quadruped, is a phenomenon contemporary at least with the acquisition of the Proccelian 

 structure in the axial skeleton of such Crocodile. 



The extent, the density, the closer fitting articulation of the bony scutal armature of 

 the Mesozoic Crocodilians, suggests its use and need in waters tenanted at the same 

 epoch by larger carnivorous marine reptiles, as, for example, the Ichthyosaurs, Plesio- 



