78 WEALDEN AND PURBECK FOSSIL FISHES. 



tends towards longitudinal ridges. The frontals are also traversed by a pair of 

 very large slime-canals. No superficial plates have been observed on the long 

 ethmoidal region. The stout parasphenoid is usually distinct crossing the orbit. 

 The cheek seems to have been covered with plates, but only those in the upper 

 part of the circum orbital ring have hitherto been clearly observed (fig. 3, co.). 

 They are narrow, four in number, the foremost the longest and tapering in front, 

 all finely ornamented with irregular tubercles of ganoine. 



The mandibular suspensorium is much inclined forwards, so that the epiadrate 

 articulation is beneath the front border of the orbit and the mouth is very small. 

 One of the bones of the pterygo-palatine arcade, either palatine or ectopterygoid 

 (PI. XVII, fig. 4), bears a close series of comparatively large and stout conical' 

 teeth. The marginal teeth of both jaws, also in close series, are slender and styli- 

 form. The maxilla, crushed and broken in the type specimen (PI. XVII, fig. 1, 

 mx ), is a rather large smooth lamina of bone, deepest behind, and not showing any 

 teeth. A fragment in another specimen (B.M. no. P. 3614), however, seems to 

 bear a very small styliform tooth. The dentary {<!.) is comparatively slender, and 

 marked by large perforations for the slime-canal. 



The opercular apparatus is complete. The preoperculum (PI. XVII, figs. 1, 2, 

 p<>[>.), which is widely expanded at the angle and has a relatively small lower limb, 

 is smooth except at the upper end, where it bears a few oblique ridges. It is 

 deeply excavated with a few large pits for the well-developed slime-canal. The 

 operculum (op.), which is about two-thirds as wide as deep, is closely ornamented, 

 except at its upper end, with coarse tubercles of ganoine which tend to fuse into 

 short ridges radiating from the point of suspension. The suboperculum (sop.), 

 which is about one-quarter as deep as the operculum, is similarly ornamented, and 

 bears a large smooth ascending process in front. The triangular interoperculum 

 (i<>p-), which is about as deep as broad, and the large upper branchiostegal rays 

 (///•.) are also ornamented in their lower portion by tubercles of ganoine which are 

 more or less fused into short oblique ridges. The extent of the branchiostegal 

 apparatus between the mandibular rami is unknown. 



The vertebral axis is usually obscured by the dense squamation, but broad well- 

 ossified vertebral rings have been seen in one fragmentary specimen (B.M. no. 

 P. 3614). 



The occipital border of the cranium is overlapped by supratemporals (fig. 1, st.), 

 of which it can only be stated that they bear a row of relatively large pits for the 

 transverse slime-canal. A large triangular post-temporal (fig.'l, ptt.) on each side, 

 as usual, supports the pectoral arch ; it is ornamented with tubercles and short 

 ridges of ganoine only at its hinder border. The supraclavicle (fig. 1, scl.) is 

 ornamented only at its upper end and above the passage of the slime-canal, ami 

 tapers to a blunt point below. The clavicle (fig. 1, cl.) is relatively large and 

 smooth, sometimes with traces of tubercles of ganoine on its posterior angle. There 



