36 FOSSIL REPTILIA OF THE 



vegetable remains, high up the cliff, 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, but of much larger size, and with the thecodont 

 implantation of the teeth. The crown belongs, in general shape, to that lamelli- 

 form, leaf- or scale-shaped type, of which the teeth of Palceosaurus, Cardiodon, 

 Hylaosaurus , Macellodon, 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 resembling spines, and ter- 

 minating respectively, or forming the confluence of, the two thickened ridges 

 (;•, 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 (Tab. VIII, fig. 2, c) and antero-posteriorly (ib., b)- 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 slightly 

 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 and rounded, so as to project from the fang ; they converge at the fore 

 and hind parts of the tooth, and unite at an acute angle (fig. 2, c, >•), to form the 

 long, basal points (fig. 3, b, s) of the serrated half of the crown. The foregoing 

 characters apply to the majority of the teeth of Echinodon. 



A portion of the left superior maxillary bone, imbedded in the matrix, with 

 its outer surface exposed, is represented in Tab. VIII, fig. l,and in outline, of the 

 natural size at «. The anterior, probably premaxillary, part has been detached 

 and broken. Three teeth, more or less fractured, project from sockets in the alveolar 

 border of this part ; their crowns are less expanded than in the typical maxillary 

 and mandibular teeth. Part of the boundary of an external nostril is indicated at «. 

 the larger maxillary fragment of the first two teeth present a similar form, and the 

 entire crown of the second shows it to be longer, as well as more slender, than the 

 posterior teeth ; it resembles a canine tooth in both shape and position, the crown 



