KIMMERIDGIAN CROCODILES. 147 



^(Kimmeridge Clay) of tlie mesozoic series to the modern Crocodilia, as exemplified 

 in the genera Crocodilus and Alligator, species of which have been restored from 

 the older tertiaries (ante Vol. I, pp. 112 — 133 ; Crocodilia, Plates 1 — 4). 



The resemblance to these genera and difference from the genus Gavialis are 

 manifested in the proportions of length and breadth of the antorbital part of the 

 skull ; and the difference from the latter existing genus and the extinct Crocodilia 

 {Teleosaurus and /Sieweosattnts), with gavialic proportions of the skull, is exemplified 

 in the extension of the nasal bones (PI. 20, fig. 1, is) to the outer nostril, «, and is 

 increased by the smaller proportional number of teeth in the upper jaw, 15, 

 (PI. 20, fig. 2), than has been noted in any existing species of Alligator or 

 Crocodile proper.^ 



Cuvier assigns to the latter genus 19 teeth on each side of the upper jaw f and 

 to the Alligators 19 or 20 teeth in the upper jaw." In both genera, the teeth are 

 signalised as of unequal size, " sont inegales " and this character, as illustrated in 

 Cuvier's ' Planche I,' is more marked than it could have been in Plesiosuchus 

 judging from the series of sockets, and the absence of the premaxillo-maxillary 

 constrictions, shown by those recent species {Crocodilus vulgaris. Croc, acutus) 

 which the fossil most resembled in the shape of the skull (PI. 20, fig. 1). 



The narial character which distinguishes the gavialic Teleosaurus and Steneo- 

 saurns from the Crocodilian fossils is shown in Plate 1, fig. la, Gavialis, and fig. 

 2a Teleosaurus, which may be compared with PI. a, 2, fig. 1 [Crocodilus suchus) 

 and PL 2a, fig. 1, Crocodilus champso'ides. The agreement in this respect with the 

 latter group is exemplified in PI. 20, fig. 1, 15 n. 



But now comes an important, perhaps more important, character differentiating 

 the present with all known mesozoic Crocodilia from all known tertiary and 

 existing kinds, gavials not excepted. It is presented by the articular surfaces of 

 the vertebral bodies or centrums ; these instead of articulating together by ball- 

 and-socket joints, are joined by surfaces deviating little from flatness, and that in 

 the dii'ection of concavity. Cuvier had recognised this character in the gavial- 

 like fossils which he described and figured from Liassic and Oolitic formations ; 

 but he was not moved thereby to frame for them generic names. 



Of the vertebral body in his ' Gavial de Caen' (Teleosaurus, Geoffroy) Cuvier 

 states : — " II a ses deux faces tres-legerement concaves, et son milieu retreci." 

 (Op. cit., p. 137), and he remarks : — " C'est la, comme on voit, un caractere fort 

 different de celui des crocodiles vivans, oil toutes les faces posterieures sont tres- 

 convexes et les anterieures tres concaves" (lb., ib.) 



1 " Les CROCODILES — proprement dits — out quinze dents de chaque cote en bas, dix-neuf en haut," 

 ' Ossemens Possiles,' torn, v, pt. ii, 4to, p. 31. 



- " Les Caiuans {AlUgatof) ont, au moins, dix-neuf et quelquefois jusqu'a vingt-deux de cliaque 

 •cote en bas ; au moins, dix-neuf, et souvent vingt en haut," lb., p. 30. 



