92 BRITISH FOSSIL REPTILES. 



transverse diameter of this part of the shaft is 2 inches 3 lines ; the fore-and- 

 aft diameter is 2 inches 6 lines. 



The fibula expands chiefly in the fore-and-aft direction at its upper end, 

 where it measures 5 inches across. Six inches lower down this diameter has 

 contracted to one of 1 inch 8 lines ; eleven inches lower it measures 1 inch 

 3 lines, the transverse diameter being 9 lines. Seven inches from the proximal 

 end the fibula presents at its outer and back part a thick, longitudinal, rough 

 ridge, for the attachment of a muscle. It continues in contact with, and gets 

 rather behind, the tibia as it descends. 



The foregoing indications of a Dinosaur in the lower Lias excited speculation 

 as to whether it had been herbivorous, like the Iguanodou of the newer Mezozoic 

 beds, or carnivorous, like the Megalosaur, which has been traced from Wealden 

 down to the Great Oolite. The structure of the femur jjointed the former way, 

 but the proof which the dentition only could give was wanting. 



The persevering encouragement afforded by Mr. Harrison to the workmen in 

 the Lias quarries was subsequently rewarded by the acquisition of the fine 

 specimen of a skull which forms the subject of Plates 45, 46, 47. 



The teeth, in their close-set, thecodont implantation, relative size to the jaw, 

 degree of expansion, and general shape of the crown, resemble those ascribed to 

 the Eijlceosaurus (Vol. i, p. 367, PI. 39) ; but the crown presents the median 

 longitudinal prominence and marginal serrations which bring it closer to the 

 Iguanodont pattern ; and, in the degree in which they depart therefrom, they 

 still more closely resemble the teeth of the Echinodon from the Purbeck, which 

 may prove to be a small kind, or young, of a Dinosaur. They, however, present 

 diS'erent proportions. 



Referring, therefore, the skull in question to the Dinosaurian order, it supplies 

 most acceptable information as to the cranial structure of that group, in addition 

 to that derived from the Iguanodon Foxii of the Wealden beds (Vol. i, p. 520, 

 pi. 49, figs. 9, 10). 



Of Megalosaurus, and Hylceosaurus, portions of lower jaw, and fragments of the 

 upper jaw, palate, and basis cranii, are all that have hitherto come to light. But 

 the present specimen is the entire skull, wanting only the fore end of the upper 

 and lower jaws. 



The cranium has been slightly crushed and distorted by oblique pressure, 

 due to movements of the matrix after imbedding and petrifaction. The right 

 halves of the mid-frontal and nasal are depressed a little below the level of the 

 left halves of the same bones, and the right diverging branch of the parietal has 

 been broken from the rest of the bone, near the median line, and dislocated by 

 the same pressure from its union with the mastoid. The right ramus of the 



