ELOPOPSIS. 135 



marked by vertical striations at the base (fig. 3 b). Behind the few foremost, the 

 teeth are remarkably uniform in size, and in the gaps between them may be seen 

 the points of developing successional teeth (Brit. Mus. no. P. 10337). Their 

 apices are frequently blunt, as if worn. The dentary bone of the mandible is 

 imperfect and not well seen in the type specimen (fig. 2 c), but is better shown by 

 a comparatively small specimen (fig. 3). It tapers in front to an almost pointed 

 symphysis, where it is thickened at the surface of contact with its fellow of the 

 opposite side. The oral border of the bone is wavy in front, and the lower part 

 of its outer face is traversed by a deep longitudinal groove, in which would 

 probably lie the slime-canal. On the edge of the dentary there is a single series 

 of sharply-pointed conical teeth, which are somewhat laterally compressed (though 

 not to sharp edges), and marked with vertical striations (fig. 3 a). In the anterior 

 convexity these teeth are quite small, but those of the rest of the series are much 

 larger than the marginal teeth of the upper jaw. The developing successional 

 teeth evidently alternate with those in function. The large inner symphysial 

 tooth (seen in fig. 2 c, its base in fig. 3) is a little laterally compressed, but nearly 

 round in section. Many sections of teeth are observable in the fossils and exhibit 

 no trace of a pulp-cavity. 



The bones of the opercular apparatus are remarkably thin, large, and smooth, 

 shoAving only a slight waviness parallel with the margins. The preoperculum 

 (fig. 2. pop.) is much expanded at the angle and in the lower limb, and bears 

 marks of slime-canals which radiate backwards from the main slime-canal of its 

 anterior border. The branchiostegal rays must have been numerous, in probably 

 not less than 20 pairs, according to the type specimen, but only the hinder 14 

 pairs are satisfactorily known (B. M. no. P. 10320). 



The vertebral centra (fig. 2 d) are strengthened by a few longitudinal ridges, 

 which extend between the stout anterior and posterior rims. They are not much 

 constricted, and none are longer than deep. The neural and hgemal arches in the 

 caudal region are much flattened from side to side, and sharply inclined backwards. 



In the pectoral arch, the clavicle, supraclavicle, and post-temporal are expanded 

 into large, smooth plates, which are thin and readily flake in the fossils. There 

 also appear to be enlarged postclavicular scales. The fins are almost unknown, 

 but the base of the dorsal in B. M. no. P. 10217, shows that it was in the middle 

 of the back, not remote. 



The scales are large, thin, and very deeply overlapping, arranged in regular 

 series. Their small exposed sector is sometimes quite smooth, sometimes impressed 

 by very small pittings (fig. 4). The lateral line does not appear to form a ridge, 

 but the canal traversed by it is conspicuous in flaked specimens. 



Affinities. — In the characters of its maxillary dentition E. crassus agrees most 

 closely with E. ziegleri, from the Cenomanian of Westphalia, but these two species 

 apparently differ in their mandibular dentition. 



