VERTEBRAL CHARACTERS OF PLESIOSUCHUS. LF 
Of the figures which he selects as illustrative of his genus Steneo- 
saurus, I append copies of figures 8 and 13. The latter (fig. 1) 
represents the upper surface of the best preserved fossil skull, one 
twelfth of the natural size; Cuvier’s fig. 8 (fig. 2) represents the 
palatal surface, one fourth the natural size. Geoffroy recognizes in 
the narial character, n, and proportions of the skull, that his Oolitic 
Steneosaurus made a nearer approach to the Gavyial than did the 
Liassic Teleosaurus. ‘‘Steneosaurus,” he remarks, ‘“‘hasnot a skull so 
long and slender as in Zeleosawrus, but longer and more slender than 
in Gavialis” ; and this character is exemplified in the Cuvierian 
figures, copied from the plate above cited. They may be compared 
with the upper and under views of the Crocodilian skull from 
Kimmeridge Bay, Dorset, given in figures 2 and 1, in plate ix. of 
the volume of our ‘ Quarterly Journal’ above cited. The mere 
rectification of a generic name would not have been deemed sufficient 
ground for this trespass on the attention of the Geological Society ; 
nevertheless, in pursuance of my official duty of labelling accurately 
the specimens arranged for public inspection in the present ‘Museum 
of Natural History, the substitution of Plesiosuchus Manselit, Ow., 
for Stencosaurus Manselii, Hulke, requires an exposition of the 
grounds; and a stronger motive for submitting them to the Geolo- 
gical Society is the interesting relation of the nearer approach to 
Tertiary Crocodilian cranial characters which is made by the pro- 
portions of the skull with the conformation of the anterior nostril, of 
the fossil from a Mesozoic formation nearer our own time than that 
which yielded Cuvier and Geoffroy their evidences of the Teleosaurian 
and Steneosaurian extinct species. 
The frontal bones of Plesiosuchus converge 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 *. This opening is ovoid, three inches and a half in length, 
three inches in greatest breadth. The premaxillaries meet and join 
an inch and a half anterior to the horizontal nostril. 
The transition to Tertiary and existing Crocodiles is manifested 
by the proportions of the skull and of the teeth ; but these, in the 
degree of general equality of size, are Gavial-like, while in relative 
size and paucity of number, in Plesiosuchus, they show the Croco- 
dilian character in excess. ‘There is no trace of an alveolar pit in 
the upper jaw for the reception of a lower canine as in the Alli- 
gators, nor of any lateral notch for such a tooth as in the Crocodiles. 
The general equality of size in the tooth-crowns seems a remnant 
of the earlier Mesozoic dental character ; but the number of teeth 
is even less than in any known Crocodile or Alligator. I add a 
brief definition of the generic formule, applicable, respectively, to 
Steneosaurus and Plesiosuchus :— 
Genus Steneosaurus, Geoff. Vertebree platyccelian ; nasals not 
* “Tes intermaxillaires, a, a (fig. 1, 2,5), entourent les narines externes, 
excepté un endroit fort étroit o la pointe des os nasaux, #, &, se place entre 
eux.” ‘ Détermination des os de la téte dans les Crocodiles proprement dits.” 
‘ Ossemens Fossiles,’ v. pt. 11. pp. 69, 71. 
