CRETACEOUS REPTILES. 383 
half the vertical diameter of the jaw; at the posterior part of the series the 
fangs sink into one-third or one-fourth the depth of the jaw. The canal, 
which, as in the Crocodile, extends below and along the inner side of the bases 
of the sockets and anchylosed fangs, is shown, filled by chalk, at d, fig. 1. Pl. 
XXXVII. Traces of the vascular foramina along the outer side of the jaw are 
visible in the right dentary piece whose outer side is exposed: the ‘splenial’ 
(‘opercular,’ Cuvier) element is shown at fig. 1, on the left ramus. 
In the portion of the left superior maxillary bone (Pl. XXXVII. fig. 1 a) all 
the teeth are, unluckily, too much broken or abraded to give an idea of the pre- 
cise form of their crowns ; they are rather more compressed at their base than in 
Mosasaurus Hofmanni: the posterior ridge is much less developed, and the whole 
of the posterior longitudinally concave border is more transversely convex than 
in Mosasaurus Hofmanni or Mos. Mazximiliani. There is as little indication of 
the angular or polygonal structure in these teeth as in those of the lower jaw; 
but the enamel shows some longitudinal striations. 
All the vertebrae of the Mosasaurus, according to Cuvier, are concave at the 
fore-part, convex at the hind-part of their bodies ; the convexity and concavity 
being greatest on the anterior vertebree. The foremost of these are characterized 
by an inferior spinous process developed from the middle of the lower surface of 
the centrum: they have two transverse and four articular processes, and a long 
compressed upper spine. The centrum is longer than it is broad, and broader 
than it is high: the terminal articular surfaces are transversely oval or reniform. 
Such are the characters of the last cervical or first dorsal vertebra. The 
middle dorsal vertebrz are like these, but have no inferior spinous process. 
Then follow vertebre which have no articular or oblique processes (zygapo- 
physes), but have longer and flatter transverse processes (diapophyses), and ter- 
minal articular surfaces of a triangular form with the base downwards. Next 
come vertebre with transverse processes and inferior processes (parapophyses) 
for the articulation of chevron-bones (hemapophyses) : afterwards vertebrae with- 
out transverse processes and with large anchylosed chevron-bones (hzmapo- 
physes) ; and finally vertebrae devoid of all processes whatever. 
The vertebre discovered in the Kentish chalk with the jaws and teeth above 
described, and of corresponding proportions with the vertebrze of the Mosasaurus 
Hofmanni, present all the generic characters of these parts of the skeleton of 
that Lacertian genus, and correspond with the third and sixth kind, or with the 
posterior dorsal and the anterior caudal vertebree, as defined by Cuvier. But the 
3D2 
