Professor Buckland on the Megalosaurus. 395. 



excepting many single teeth and a fragment of the lower jaw. See Plates XL. 

 and XLI. 



Mode of Dentition : see Plates XL and XLL, figs. \, 2. — The teeth are 

 lodged in distinct alveoli^ but do not adhere, as in the monitors, by any incor- 

 poration of the root or sides with the substance of the jaw ; the young teeth 

 are hollow at the base, and, as usual, become filled as they grow older. 



The new teeth are formed in distinct cavities by the side of the old ones 

 towards the interior surface of the jaw, and probably expel the old teeth 

 by the usual process of pressure and absorption, and insinuate themselves 

 into the cavities thus left vacant. The teeth are flattened laterally, and 

 recurved backwards, being serrated on the posterior edge along the whole 

 extent of their enamel, and also on the anterior edge when young ; this edge 

 is thicker, and, like the back of a knife, is more solid than the posterior or cut- 

 ting edge. 



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 interior of the alveoli. From the centre of each triangular 

 plate, a bony septum crosses to the outer parapet, thus completing the alveolus. 



The new teeth rise in the angle between each triangular plate. The exte- 

 rior surface of the jaw (Plate XLL fig. 2.) presents several distinct and rugose 

 cavities for the passage of the exterior branches of the inferior maxillary blood- 

 vessels and nerves. This character agrees, not with the crocodiles, but with 

 the other members of the saurian family. 



From the absence of any curvature in this fragment of the anterior extre- 

 mity, (which is nearly one foot in length,) it is obvious that the lower jaw 

 must have terminated in a flat, straight, and very narrow snout. 



The exuberant provision in this animal for a rapid succession of young 

 teeth, to supply the place of those which might be shed or broken, is very 

 remarkable ; it seems also, that a small number of teeth only were in use at 

 the same time. 



Vertebra. — The bones that we have as yet discovered of the vertebral column, 

 are confined to five anchylosed joints, including the two sacral, and two others 

 which are probably referable to the lumbar and caudal vertebrae. They are 

 all much contracted in the middle, and have a deep fossa immediately beneath 

 the annular part. See Plate XLIL 



Although we are without any dorsal vertebrae, we fortunately possess ribs 

 (see Plate XLIIL figs. i. 2.) which have a double articulation at their head, 

 as in the crocodile. 



