104 REPORT — 1841. 



The essential characters of the most authentic of these remains prove the 

 Megalosaurus to have been closely related to the Lacertian division of the 

 Saurian order ; but the teeth, the vertebrae, and some of the bones of the ex- 

 tremities, indicate its affinities to the Crocodilian group, and all these parts 

 manifest more or less stronglj' the peculiar characters of its own remarkable 

 family. In the instructive and characteristic portion of the lower jaw, the 

 sockets, like the teeth, are compressed, and are separated by complete parti- 

 tions ; but they are so much wider than the teeth, as to suggest the existence 

 of a greater proportion of ligamentous gum at the upper part of the alveolar 

 tract in the recent animal than in the Crocodiles. " The outer rim of the 

 jaw rises almost an inch above the inner rim, and forms a continuous lateral 

 parapet, supporting the teeth externally ; whilst the inner rim throws up a 

 series of triangular plates of bone, forming a zigzag buttress along the in- 

 terior of the alveoli. From the centre of each triangular plate, a bony septum 

 crosses to the outer parapet, thus completing the alveolus*." There is a 

 slight groove and ridge along the inner side of the sockets, and it is at this 

 groove, at the interspace of each triangular plate, that the apices of the new 

 teeth protrude. The teeth have compressed, conical, pointed crowns, with 

 trenchant and serrate anterior and posterior edges. They appear straight 

 when they first protrude, but are bent in the progress of growth ; in the course 

 of development the crown of the tooth is solidified, and the anterior margin 

 at the base of the crown becomes smooth and convex. The smooth enamelled 

 surface of the tooth presents fine polished wrinkles. 



In all existing Lizards the teeth are anchylosed, either to the side of an 

 outer alveolar parapet, according to the pleurodont type, or to its summit, ac- 

 cording to the acrodont type. The double parapet, inclosing and concealing 

 the germs and the bases of the full-grown teeth, is a remarkable approach in 

 the present gigantic Dinosaur to the Crocodilian structure, the similarity in 

 this respect no doubt resulting from a similar necessity in the carnivorous 

 Megalosaur for a firm lodgment of the destructive maxillary weapons. The 

 higher development of the outer alveolar parapet bespeaks the affinity of the 

 Megalosauriis to the Lizards : in the form of the teeth it approaches nearest 

 to the Varanian family, which at the present day includes the largest, and most 

 carnivorous species of Lizard. 



VertebrcE. — The Megalosaur deviates more decidedly from the existing Mo- 

 nitors and Lizards in its vertebral characters. These are afforded, at present, 

 by the sacral, a few costal and caudal vertebrae. The articulating surfaces of 

 the body of the vertebra are nearly flat or slightly concave, as in the ccelospon- 

 dylianf Crocodiles. The non-articular surface is remarkably smooth and po- 

 lished. The body is much contracted in the middle : the margins of the ex- 

 panded articular extremities are thick and rounded off". The middle contracted 

 part of the body is nearly cylindrical, being nipped in, as it were, by a more 

 or less deep longitudinal fossa on each side, just below the base of the neural 

 arch, but again slightly expands to support that part. The length of the base 

 of the neurapophysis is nearly equal to that of the centrum : the suture is per- 

 sistent, as in Crocodiles ; its course is undulating, and it rises in the middle. 

 The neurapophysis ascends and inclines outwards, to form, at a height above 

 the centrum equal to three-fourths its vertical diameter, the margin of a broad 

 platform of bone, from the sides of which the transverse processes are deve- 

 loped, and from the middle part the spinous process. A strong ridge or but- 

 tress of bone extends from the posterior angle of the base of the neurapophy- 



* Transactions of the Geological Society, 2nd Series, vol. i. p. 395. 

 t I find this collective term convenient in application to those Crocodilians which have 

 the vertebrae concave at both ends. 



