THE HYLiEOSAURUi?. 323 



have the bilobed head, as in the crocodiles, asso- 

 ciated with the arched and rounded process of the 

 lizards, and an enormous expansion of the bone at 

 its spinal curvature. This reptile possessed a very 

 formidable dermal covering : it had rows of ellip- 

 tical and circular dermal bones along each side of 

 the vertebral column, and appears to have been 

 armed with a series of angular spines of great size, 

 arranged along the middle of the back ; in the same 

 manner as the dorsal fringe of the Iguana. The' 

 structure of the bone composing these dermal 

 processes, closely resembles that of the ligamentous 

 fibres of the corium, or skin, and seems to have 

 resulted from an ossified condition of the dermal 

 integument. A few detached vertebra? of the 

 Hylasosaurus, recognisable by their perfectly cir- 

 cular and nearly flat extremities, have been found 

 in the Weald clay at Brixton.* 



Megalosaurus.-J- — This name was given by Dr. 

 Buckland to an enormous reptile, of which teeth 

 and bones were first observed in the oolitic lime- 

 stone of Stonesfield, near Oxford, and afterwards 

 in the Wealden strata. The teeth present a 

 striking contrast to those of the Iguanodon ; they 



* See " Medals of Creation," p. 734, and " Memoirs on the Fossil Reptiles 

 discovered in Tilgate Forest." Philos. Trans. Part II. for the year 1841. 

 t See Dr. Buckland's Bridgewater Essay. 



