Page:Quarterly Journal of the Geological Society of London, vol. 34.djvu/504

422 ball-and-socket articulation of the trunk-vertebræ better adapts that part of the body to be sustained and moved in air than the amphicœlian articulation which characterizes the vertebral column of the more aquatic, and probably marine, Crocodiles of the Mesozoic periods.

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 procœlian 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 signalized by Cuvier as "l'espèce la mieux cuirassée de tout le genre".

But the Goniopholis of the Wealden and Purbeck formations surpassed even the Teleosaurus cadomensis and its congeners in this part of its organization.

The great quadrangular dorsal scutes of Goniopholis are distinguished 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 repeating 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.

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. No 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 fortunate than their predecessors in respect to possible hostile fellow-denizens of the deep.

Certain it is that the defensive armour of procœlian 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