132 WEALDEN AND PQRBECK FOSSIL FISHES. 



tudinal ridges, producing a striated appearance on superficial view. When a 

 centrum is isolated and exposed on the articular face (PI. XXV, fig. 3), a median 

 perforation is seen for a persistent strand of the notochord. All the abdominal 

 vertebral centra are deeper than long, with gently rounded sides, and their 

 appended arches are loosely articulated. The foremost centrum is not united with 

 the basioccipital, but (as shown in PI. XXIV, fig. 4<) it is peculiar in consisting of 

 two fused discs, which are limited by a sharp line, the front disc bearing a slight 

 prominence above for the support of the first neural arch, the second bearing a 

 similar pair of slight prominences below to carry the first pair of ribs. The 

 second centrum (sometimes also the third centrum) again exhibits prominences, 

 but all the other abdominal centra are pitted for the reception of both the neural 

 arches and ribs. The caudal vertebral centra are more elongated, about as long 

 as deep, and their secondary ossification is disposed so as to form a sharp median 

 longitudinal ridge on each side. Their appended arches are more firmly fixed in 

 the sockets than those in the abdominal region, even if they are not fused. The 

 arches are almost destroyed in the type specimen, but they are seen in others, as 

 in the fragment represented in PI. XXIV, fig. 5 The neural arches are compara- 

 tively small and delicate, and unite by large anterior zygapoph} r ses, but they are 

 obscured in the abdominal region by the numerous well-developed intermuscular 

 bones which overlie them. In the caudal region the neural and haemal arches are 

 nearly symmetrical, and sharply curved backwards, and a few intermuscular bones 

 occur both above and below the vertebral centra. The stout gently-curved ribs 

 extend to the ventral border of the fish, each with a slightly expanded articular 

 head and a wide groove along its anterior or outer face. 



The stout clavicle, of which the upper half is shown in PI. XXV, fig. 1 (<*/.), 

 bears a large lateral expansion which is nearly smooth, only marked by a few 

 vertical ridges and grooves or wrinkles at the upper end. The long and narrow 

 supraclavicle (scl.) is similarly ridged, and traversed by a large slime-canal. The 

 pectoral fin must have been relatively large, its rays when adpressed to the trunk 

 (as in the type specimen) reaching two-thirds of the distance to the insertion of 

 the pelvic fins. The pelvic fin-supports (PI. XXIV, fig. 5, ph.) are long and 

 narrow laminas, widest at the articular end, tapering forwards, strengthened by a 

 rib-like thickening along the outer edge, and apparently fixed together along the 

 thin inner edge. The pelvic fin-rays, about 10 in number, are deeply imbricating 

 and closely articulated distally. The dorsal and anal fins are shown in the type 

 specimen to be acuminate in front and directly opposed, but their details are better 

 seen in other specimens. In the dorsal fin there are about 18 rays, of which the 

 anterior four are simple and gradually increase in length, while the fifth is the 

 longest, and this and the following are divided and articulated distally (B.M. 

 no. P. 4536). The foremost support is fan-shaped, bearing the first three rays 

 (PI. XXIV, fig. 5, d.), and the other supports are winged at the articular end. 



