98 BRITISH FOSSIL REPTILES. 



the decreasing size of tlie anterior teeth, makes it more probable that but a small 

 proportion of the muzzle is wanting in the present specimen. 



Removal of matrix from the hinder interspace of the mandibular rami exposed 

 a ceratohyal, 3 inches in length, 4 lines in breadth, of a slight sigmoid flexure, 

 the hind part bending up to between the angle of the mandible and the atlas 

 vertebra ; as no trace of basihyal was foimd, this element was probably cartilaginous, 

 like that broad one in the tongue-skeleton of the crocodile.' 



The specimen of SceUdosaurus here described has been buried and petrified 

 with the mouth shut ; there has been no dislocation of the under jaw, and the 

 skull shows that the teeth of the upper jaw overlapped and concealed those of 

 the lower. The crowns of both series were a little inclined inward, as shown at 

 the fractured fore part (PI. 46, fig. 2, a b,) ; there is a similar inclination of the 

 alveolar plates. 



The teeth are small, or of Lacertian proportions to the jaws ; they are numerous 

 and close-set, implanted in sockets (ib. a) forming an uninterrupted series along 

 the alveolar border. The faug is simple, and longer than the crown, presenting 

 a full ellipse in transverse section, and projecting a little beyond the socket. In 

 the upper jaw the crown (PI. 46, fig. 3, magn.,) begins by bulging outward, with a 

 smooth convexity subsiding as it gradually expands, and dividing to be continued 

 along the middle and the margins, with intervening concavities, producing an 

 undulated surface across the broadest part of the crown. The marginal con- 

 vexities or ridges terminate each in a point at the broadest part of the crown ; 

 whence, the plate-shaped tooth having thinned off to an edge, this is divided on 

 each side into five or six smaller points ; these denticulate margins converge 

 straight, at an angle rather less than a right one, to the apex of the tooth, which 

 is formed by the pointed termination of the median convexity. The crown is 

 coated by a polished enamel, of jet blackness in the fossil, smooth under the 

 lens upon the convexities, finely punctate in the hollows of the expanded part of 

 the crown. The whole tooth in the upper jaw is very slightly bent backward, 

 with as slight an oblique twist, making the hinder angle overlap, in some, the 

 front angle of the crown of the tooth behind. 



The inner surface of the hind teeth exposed in the right ramus of the jaw 

 (PI. 47, fig. 2) shows similar configuration of the crown to that of the outer 

 surface of the teeth above ; but with a larger proportion of the serrated part, and 

 with the borders less equal, the anterior one showing as many as nine points. 



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 



1 ' Archetype of Vertebrate Skeleton,' 8vo, 18i8, p. 121, fig. 22, 40. 



