14 FOSSIL REPTILIA OF THE LOWER LIAS. 



On the left side, in an extent of the alveolar border of the upper jaw measuring 

 4 inches, there are nineteen sockets, and only one tooth missing. On the right 

 side, in an extent of 3| inches, there are sixteen sockets, and three teeth missing. 

 The fractured part of the jaw yields evidence of the usual reptilian provision for 

 successional teeth in reserve alveoli, containing tooth-germs, at the inner side of 

 the base of the teeth in place (Tab. V, fig. 2, c). The teeth gradually increase in 

 size from the hindmost to the fifth in advance, continue of about the same size 

 to the tenth, and then gradually decrease in size to fractured fore part of the jaw. 



Were the serrated borders of the terminal half of the crown to be worn down, 

 the teeth of Scelidosaurus would be like those referred to Hylceosaurus in my 

 Monograph of 1856.* There is no evidence, however, that any of them have been 

 so worn down ; in this respect they resemble more the teeth of Echinodon, the 

 upper teeth in Scelidosaurus differing chiefly in the proportions of length to 

 breadth of the crown. Whether the anterior teeth had the simple laniariform 

 character at the fore part of the jaws in Scelidosaurus, as in Echinodon, remains 

 to be proved. The finely and sharply serrated and pointed teeth of the Scelidosaurus 

 glided upon each other, the upper on the outerside of the under, like the blade- 

 shaped crowns of the carnassials of feline mammals ; and yet the similarity of the 

 teeth, in their number and uniformly small size, to those of the modern Iguanas 

 suggests that they may have been put to like uses. The compressed, serrate 

 crowns in those herbivorous lizards worked obliquely upon each other, in a similar 

 scissor-blade way. In Iguanodon the dentition is obviously modified more 

 decidedly for mastication of vegetable substances. In Scelidosaurus it is adapted 

 for division of such substances, but it would be equally effective in piercing and 

 cutting or tearing through animal textures. 



If this Dinosaur occasionally went to sea in quest of food, it may be expected 

 to present in the fore part of the jaws, wanting in the present specimen, laniariform 

 teeth, as in Echinodon, for the prehension and retention of living prey. Should 

 these prove to be absent, and the dental series to begin as it ends, it will in- 

 cline the balance of probability to the phytophagous nature of the Liassic 

 Scelidosaurus. 



* * Monograph on Wealden Reptilia,' p. 21, tab. viii, tigs. 6 — 9. 



