182 GIGANTIC TERRESTRIAL SAURIANS. 



marrow, while their cylindrical form tended also to connbine 

 this lightness with strength.* 



The form of the teeth shows the Megalosaurus to have 

 been in a high degree carnivorous : it probably fed on 

 smaller reptiles, such as Crocodiles and Tortoises, whose 

 remains abound in the same strata with its bones. It may 

 also have taken to the water in pursuit of Plesiosauri and 

 fishes.f 



The most important part of the Megalosaurus yet found, 

 consists of a fragment of the lower jaw, containing many 



* The medullary cavities in (lie fossil bones of llie Megalosaurup, from 

 Stonesfield, are usually filled with calcareous spar. In the Oxford Museum 

 there is a specimen from the Wealden fresh-watcr formation at Langton, near 

 Tunbridge Wells, which is perhaps unique amongst organic remains: it pre- 

 sents the curious fact of a perfect cast of tlie interior of a large bone, ap- 

 parently the femur of a Megalosaurus, exliib;ling the exact form and ramifi- 

 cations of the marrow, whilst the bone itself has entirely perished. The 

 substance of this cast is fine sand, cemented by oxide of iron, and its 

 form distinctly represents all the minute reticulations, with which the mar- 

 row filled the inlercoluminations of the cancelii, near the extremity of the 

 bone. It exhibits also casts of the perforations along the internal panetes, 

 whereby the vessels entered obliquely from the exterior of the bone, to com- 

 municate with the marrow, A mould of the exterior of the same bone has 

 been also formed by the sandstone in which it was imbedded; hence although 

 the bone itself has perished, we have precise representations both of its ex- 

 ternal form and internal cavities, and a model of the marrow that filled 

 this femur, nearly as perfect as could be made by pouring wax into an 

 empty marrow bone, and corroding away the bone with acid. The sand 

 which formed this cast must have entered the medullary cavity by a frac- 

 ture across the other extremity of the bone, which was wanting in the spe- 

 cimen. 



From this natural preparation of ancient anatomy we learn that the dis- 

 position of marrow, and its connexion with the reticulated extremities of the 

 interior of the femur, were the same in these gigantic Lizards of a former 

 world, as in medullary cavities of existing species. 



t Mr. Broderip informs me that a living Iguana (I. Tuberculata,) in the 

 gardens of the Zoological Society of London, in the summer of 1834, was 

 observed frequently to enter the water, and swim across a small pond, using^ 

 its long tail as the instrument of progression, and keeping its fore-feet mo- 

 tionless. 



