422 PROP. E. OWEN ON THE MODIFYING INFLUENCE 



ball-and-socket articulation of the trunk- vertebrae better adapts 

 that part of the body to be sustained and moved in air than the 

 amphiccelian articulation which characterizes the vertebral column 

 of the more aquatic, and probably marine, Crocodiles of the Meso- 

 zoic periods. 



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

 which, in later Tertiary and modern times, might tempt a Croco- 

 dile to rush on shore in pursuit of a mammalian quadruped, is a 

 phenomenon contemporary at least with the acquisition of the pro- 

 ccelian structure in the axial skeleton of such Crocodile. 



The extent, the density, the close-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, Pliosaurs, 

 Polyptychodonts, and Mosasaurs. The Oolitic species of Crocodile 

 (" Crocodile de Caen," Cuv. ; Teleosaurus cadomensis, Geoff.) is sig- 

 nalized by Cuvier as "l'espece la mieux cuirassee de tout le 

 genre"*. 



But the Goniopholis of the Wealden and Pur beck formations sur- 

 passed even the Teleosaurus cadomensis and its congeners in this 

 part of its organization. 



The great quadrangular dorsal scutes of Goniopholis are distin- 

 guished by the presence of a conical process continued from one 

 of the angles transversely to the long axis of the scute, like the 

 peg or tooth of a tile, which fits into a depression on the under 

 surface of the opposite angle of the adjoining scute, thus serving to 

 bind together the plates of the imbricated bony armour, and re- 

 peating a structure which is characteristic of the large bony and 

 enamelled scales of many extinct ganoid fishes. The hexagonal 

 ventral scutes of Goniopholis were firmly joined together by broad 

 sutural borders f. 



No knight of old was encased in jointed mail of better proof than 

 these Crocodiles of an older world. 



But the inimical contemporaries of these Crocodiles passed away. 

 INo representative of Mosasaurian, Plesiosaurian, or Ichthyosaurian 

 families lived after the Secondary epoch. Crocodiles alone, of the 

 larger aquatic Saurians, continued on to the present time, more for- 

 tunate than their predecessors in respect to possible hostile fellow- 

 denizens of the deep. 



Certain it is that the defensive armour of procoelian Crocodiles 

 has degenerated. Bony ventral scutes are exceptional in them $, 

 and the dorsal ones are fewer, thinner, less closely arranged and less 

 firmly connected with one another. And if this change can be 



* ' Ossemens Fossiles,' 4to, torn. v. pt. 2, p. 139 ; also Eugene E. Deslong- 

 eharaps, ' Notes Paleontologiques,' 8vo, 1860, pi. xiii. 



t "Keport on British Fossil Keptiles," Reports of British Association, 8vo, 

 1841, p. 70. 



\ Observed by Natterer in certain South- American Alligators. " Beitrag zur 

 naheren Kenntniss der siidamerikanischen Alligatoren," Ann. Wien. Mm, 

 t. ii. (1840) p. 313. 



