126 BRITISH POSSIL REPTILES. 



SUPPLEMENT No. II. 

 MESOZOIC LIZARDS. 



Genus — Echinodon,'' Oiven. 



EcHiNODON Becclesii, Owen. ' Lacertilia,' PI. 11, figs. 1 — 9. 



The specimens figured in the above-cited plate were discovered by S. H. 

 Beccles, Esq., F.R.S., in the thin, fresh-water stratum at Durdleston Bay, Isle of 

 Purbeck. They consist of portions of the upper and lower jaws of a Saurian, 

 allied, by the shape of the teeth, to Macellodon (PI. 11, fig. 10, a—e),^ but of larger 

 size, and with the thecodont implantation of the teeth. The crown belongs, in 

 general shape, to that type, of which the teeth of Palceosmirus, Scelidosaurus, 

 Gardiodon, HylcBOsaurus, and even those of Iguanodon, are modifications. The 

 teeth of the present genus are distinguished by the marginal serrations of the 

 apical half of the crown, which increase in size from the apex to the base of that 

 angular part of the tooth, the two basal points resembhng spines, and terminating 

 respectively, or forming the confluence of, the two thickened ridges (ib., r, fig. 2, c) 

 bounding the fore and hind borders of the basal half of the crown. 



The crown is supported on a subcylindrical fang, and suddenly expands, both 

 transversely (PI. 2, fig. 11, c) and antero-posteriorly (ib., j). In the former 

 direction it as quickly begins to contract, and the outer and inner sides converge 

 in almost a straight line to the apex ; in the latter direction the crown continues 

 expanding for about half, or rather more, of its longitudinal extent, with a shghtly 

 convex contour; it then rapidly contracts to the apex, the converging borders 

 meeting at a right or somewhat acute angle, and being serrated as above described. 

 The thickest mid-part of the crown forms a longitudinal rising, usually more 

 marked on one side of the tooth ; at the apical half the crown gradually becomes 

 thinner towards the fore and hind margins ; but at the basal half these margins 

 are thickened, and cause the surface between them and the mid-rising to be 

 undulated transversely. At the apical part of the tooth both the outer and inner 

 sides are gently convex, the transverse section giving the thin-pointed ellipse, 



as in fig. 6, b. 



The outer and inner enamelled sides of the crown each describe a curve at their 

 base (fig. 3, b,r), convex towards the fang; these bases are somewhat thickened 



1 'Ex'tt'os, hedgehog, and oSows, tooth, "prickly tootb." 



2 ' Quarterly Jouraal of the Geological Society,' No. 40 (1S54), p. 422. 



