GIANT LAND REPTILES OR DINOSAURS. 12 



chambers, thus illustrating a principle of construction 

 well known to engineers. A similar feature is known 

 elsewhere only in birds, where these chambers are 

 filled with air. We must not, however, omit to men- 

 tion that similar chambers occur in the vertebras of 

 the smaller members of the group under consideration, 

 the reason for which is less easy to see. 



The third great group of Giant Land Reptiles was first 

 definitely brought under the notice of the scientific 

 world by the late Dean Buckland, the celebrated Pro- 

 fessor of Geology in the University of Oxford, as far 

 back as the year 1824 The Professor had observed 

 that in the Stonesfield slate of Oxfordshire, to which 

 allusion has already been 

 made, there were not uncom- 

 monly found teeth of the 

 peculiar type of the one shown 

 in woodcut 35 ; although 

 many of them were of con- 

 siderably larger dimension 

 than the figured specimen. 

 It will be seen from the 

 figure that this type of tooth 

 (of which only the crown or 



exposed portion is represented) differs very widely in- 

 deed from the teeth of the Iguanodon and Hoplosaur. 



Thus the crown of this tooth is much flattened from 

 side to side, with sharp, cutting fore-and-aft edges, of 

 which the front one is highly convex, while the hinder 

 one is either nearly straight or somewhat concave. 



FIG. 35. Profile and side of the 

 crown of a tooth of a Megalo- 

 saurian Reptile, with part of the 

 serrations enlarged. 



