DINOSAURIA. 289 



saurus, also from Stonesfield oolite, from which the inner wall 

 has been removed to shew the germ of a successional tooth c, 

 about to succeed an old tooth a, which has been broken, and 

 near to which is a newly-formed tooth b, coming into place. 

 These teeth will exemplify the shape of the crown of the tooth, 

 which is subcompressed, slightly recurved, sharp edged, and 

 sharp pointed, the edges being minutely serrated ; the edge 

 upon the convex or front border b becomes blunted as it 

 descends about two-thirds of the way towards the base of the 

 tooth ; that upon the concave hinder border a is continued to 

 the base. The lower half of the crown is thicker towards the 

 fore margin than towards the hind one ; so that a transverse 

 section, like that above a, in fig. 98, gives a narrow oval form 

 pointed behind. The crown is covered by a smooth and 

 polished enamel, which wholly forms the marginal serrations. 

 The base of the tooth is coated with a smooth, light-coloured 

 cement, forming a thin layer, and becoming a little thicker 

 towards the implanted end of the tooth. The main body of 

 the tooth consists of dentine, of that hard unvascular kind of 

 which the same part of the teeth of existing crocodiles and 

 most mammals is composed. The remains of the pulp are 

 converted into osteo-dentine in the basal part of the com- 

 pletely formed tooth. Moderately magnified, the surface of 

 the enamel presents a finely wrinkled appearance. The 

 marginal serrations shew, under a somewhat higher power, 

 that the points are directed towards the apex of the tooth — 

 a structure well adapted for dividing the tough tissues of the 

 saurian integument. 



A series of teeth from individual Megalosaurs, of different 

 ages, are preserved in the British Museum and in the geolo- 

 gical museum at Oxford ; although differing in size, they 

 preserve the characteristic form above described. In one 

 specimen the point of the crown and the trenchant margins 

 have been rubbed down to a smooth obtuse surface ; it seems 



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