656 BRITISH FOSSIL REPTILES. 



In Mr. Beckles' collection further evidence of Nuihetes destrncior is afforded by the 

 portions of jaw (PI. 43, figs. 13 and 14) and by numerous detaclied teeth, ranging in size 

 from a length of enamelled crown of 5 mm. to 20 mm. (fig. 15, c), and with variations 

 in the proportion of length to basal breadth (comp. fig. 15, d, e, with a, h). 



The teeth in the mandibular fragment accord in size and shape with those of the 

 original or type specimen -^ they are laterally compressed, strongly recurved, and combine 

 a basal fore-and-aft breadth of 3 mm. with the length of 5 mm. (straight). They 

 likewise show the " excavation or longitudinal depression on the side of the base." 

 The coronal enamel does not extend over this depression, but is continued along its 

 margins, and to a greater extent on that next the convex border of the crown than on the 

 opposite side. In the portion of jaw, originally figured, with seven more or less perfect 

 tooth-crowns, two of these indicate a longer and more slender shape than the rest- 

 Several detached teeth of this type have been exposed in portions of the ' Feather-bed 

 Marl ' in the Becklesian series. Some of these, exemplifying difference of size, are 

 figured in Plate 43, fig. 14. 



In all these tooth-crowns the characteristic fore and hind finely denticulate ridges are 

 discernible, as shown in the magnified view (fig. 16) ; the rest of the enamel is smooth 

 and even, as in the type of Nuihetes destructor. Of this species I am disposed to regard 

 the specimens above described as indicative of the range of size according to growth of 

 individuals rather than as exemplifying specific modifications of the genus. 



Dermal Bones (' granicones '). 



In many portions of the matrix of the ' Feather-bed ' are ossicles of a conical shape, 

 the cone showing various degrees of elevation, with a granulate surface, the base being flat 

 and smooth, or faintly and minutely pitted. These ' granicones ' I regard as dermal bones. 



In PI. 43, fig. 18, is represented a 'granicone' with a basal breadth of 8 mm. 

 and a length or height of cone of 14 mm. In fig. 19 the base is oblique, reducing the 

 shortest side of the cone to a height of 8 mm. In this, as in some of the similarly shaped 

 ' granicones,' part of the basal margin is raised or prominent, sometimes formed by a single 

 series of close-set granules, as in fig. 20. Those on the surface of the cone are less 

 regularly disposed, but at some parts affect a longitudinal arrangement (fig. 21.) The 

 apex shows various degrees of obtuseness, which finally reduces the granulate or exterior 

 surface of the cone to a moderate convexity, but the conical shape is the rule. The 

 smallest of such ' granicones ' has a basal breadth of 3 mm., a length of 5 mm. 



Slices of these enigmatical fossils prepared for the microscope (figs. 22, 23) demon- 

 strated the absence of the structures characteristic of piscine dermal bony cones and spines. 



1 'Quarterly Journal of the Geological Society,' 1854, p. 120. 



