NEORHOMBOLEPIS. 89 



(fig. 1, a'.) may be the interoperculum, while traces of broad branchiostegal rays 

 are seen on the left (fig. 2, br.). The supposed interoperculum, which is exposed 

 from the inner face, is about twice as long as its greatest depth. 



Traces of ossified centra, perhaps only cylinders, are seen throughout the 

 vertebral column ; and in the middle of the fish, where the column is dislocated, 

 they are well displayed in side view (v.). They are smooth, mostly as long as 

 deep, not mesially constricted, but laterally compressed above and below to a 

 longitudinal ridge for the support of the arch. Some of the neural arches are 

 seen to be not completely fused with the centra ; and two of those in the anterior 

 part of the caudal region exhibit the relatively small and slender neural spine 

 (u. a.) bent sharply backwards from the deep pedicle. 



In the pectoral arch the supraclavicle (fig. 1, scl.) is relatively large, three times 

 as deep as wide, truncated and hollowed at the upper articular end, bluntly rounded 

 below. Its exposed portion bears large flattened tubercles of ganoine, which are 

 partly fused together. The slender clavicle, as far as seen on the left side 

 (fig. 2, cl.), is not enamelled. The rather large postclavicular scales (figs. 1, 2, pel.), 

 so far as preserved, are completely covered with ganoine except at the overlapped 

 margin, and are partly ornamented with coarse flattened rugge and tuberculations. 

 They are evidently arranged as in the typical Eugnathus, the uppermost being 

 the largest, deep and triangular, its apex extending upwards somewhat above the 

 lower end of the supraclavicle. As shown on the left side, the pectoral fin 

 (fig. 3, pet.) comprises a few more than 20 rays, of which each is undivided in its 

 proximal two-thirds but becomes very finely branched and articulated distally. 

 The foremost ray is enlarged at its proximal end where it projects upwards above 

 the others ; and it is fringed with elongated, deeply overlapping fulcra, of which 

 the two uppermost are the stoutest and must have been in direct contact with the 

 basal supports. Both the fulcra and some of the anterior fin-rays bear traces of 

 ganoine. On the right side of the fossil, only two fragments of the pectoral fin 

 remain (fig. 1, pet.), but the characteristic elongated fulcra are seen fringing the 

 articulated distal portion. Of the other fins merely imperfect traces of the dorsal 

 (d.) and caudal (r.) are exposed. 



The principal scales of the flank and some of the narrow ventral scales in the 

 abdominal region exhibit a very fine sparse pitting of the enamel and a regular 

 delicate serration or pectination of the hinder border, but the other scales are 

 smooth. They are most deeply overlapping, with the best developed peg-and- 

 socket articulation, on the anterior part of the flank. Very few of the flank-scales 

 are as deep as broad, most being longer than deep, and those near the ventral 

 margin especially elongated. Many of the ventral scales in the abdominal region 

 are subdivided into small irregularly rhombic scales which only slightly overlap 

 (fig. 3). Some of the scales of the lateral line are pierced by a simple short 

 vertical slit. 



Horizon and Locality. — Wealden : Hastings, Sussex. 



12 



