VERTEBRAL CHARACTERS OF PLESIOSUCHUS. P55 
is more definitely exemplified by the extension of the nasal bones 
(see plate ix. vol. xxvi. Quart. Journal, 1870, p. 172) to the outer 
or anterior nostril; and the difference from Stengosaurus is increased 
by the smaller number of teeth—15 on each side of the upper jaw 
—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 ; and to the Alligators 19 or 20 teeth in the upper jaw. 
In both genera the teeth are signalized as of unequal size. But 
this proportional character is absent in the fossil skull now in the 
exhibited series of the British Museum of Natural History, when 
tested by the size of the series of sockets and by the absence of the 
premaxillo-maxillary constrictions shown in the species (Crocodilus 
vulgaris and Croc. acutus) which the fossil most resembles in the shape 
of the skull. A more important character of difference, in the 
comparison with Tertiary and existing Crocodilia, is shown by 
portions of vertebre attached by matrix to the skull and of size 
corresponding thereto; it is presented by the articular surfaces of 
the centrum, which deviate little from flatness, and that in the 
direction of concavity. One of these vertebre includes, with a 
great part of the centrum, the neural arch and spine; the latter 
shows its obtuse free termination. The total height of the vertebra 
is 9 inches; that of the neural arch, spine inclusive, is 64 inches, 
the neural spine being 4 inches in length. The frontal bones 
converge forwards to a point ten inches distant from the premaxillary 
apex of the skull; the nasal bones gradually narrow to a point 
penetrating the hind border of the nostril, as shown in figure 2 of 
the plate ix. (Quart. Journal, 1870) above cited. 
Cuvier had shown in all the evidences of fossil Crocodilia from 
the quarries of Oolitic stone in the vicinity of Caen, in which the 
conformation of the outer or anterior nostril was demonstrable, that 
it was bounded exclusively by the premaxillary bones, the nasals end- 
ing in a point between the maxillaries (fig. 1, n, p. 156), and at some 
distance from the premaxillaries and from the nostril which those 
bones exclusively bounded *. In this he pointed out their resem- 
blance to the modern Gharrials, as well as in the length and slen- 
derness of the upper jaw. A difference of aspect in the outer 
nostril was also indicated by these fossils, from which was inferred 
their specific difference f. 
Geoffroy, in his Memoirs on these Crocodilian Fossils t, connoted 
such distinctions by generic names; but their chief value in relation 
to the present paper consists in the characters which he gives and illus- 
trates of the fossils which he separated from those to which he gave the 
name of T'eleosaurus, to represent, or form types of the genus to which 
he applied the name of Steneosaurus. Cuvier had associated reduced, 
but accurate and instructive, views of the original fossils of both 
* «Ossemens Fossiles,’ 4to, 1822, tom. v. pt. 2. 
tT Id. ib. p. 134. 
{ “ Divers Mémoires sur des Grands Sauriens, &c.” Lu 4 l’Académie Royale 
des Sciences, le 4 Octobre, 1830. 
