32 WEALDEN AND PURBECK FOSSIL FISHES. 



upper ami anterior portions are sparsely ornamented with tubercles, wliicli fuse 

 together more or less irregularly and rarely spread over the whole plate. The 

 suboperculum is usually about one-quarter as deep as the operculum, with a 

 relatively large ascending process in front, and sparsely tuberculated near the 

 anterior and inferior margins (PI. V, fig. 8, sop. ; PI. VI, sop.). The iuter- 

 operculum is small, elongate-triangular in shape, also sparsely ornamented with 

 large irregnlar tubercles (PI. V, fig. 8, lop. ; PI. VI, iop.). Only four branchio- 

 stegal rays have 1)een clearly seen (PL V, fig. 8, />/•.), though there appear to be 

 traces of two or three more in the original of PI. VI. The uppermost is largest 

 and bears a few tubercles, while the others are smooth. There is no gular plate. 



The notochord must have been persistent, and there are no surrounding 

 ossifications. The neural and hfemal arches are incompletely ossified, so that they 

 appear hollow and are frequently crushed in the fossils. The neural spines in the 

 abdominal region so far back as the origin of the dorsal fin, are stout and a little 

 widened distally where they nearly i^eacli the dorsal border (PI. VII, fig. o, n) : 

 they appear to be slightly curved, with the concavity forwards. The neural spines 

 in the caudal region are shorter and more slender. The ribs (/•.) are round or 

 ovoid in section, comparatively slender, and extend almost to the ventral border. 

 The hsemal arches within the base of the caudal fin are especially stout and 

 somewhat expanded distally (as seen in B. M. no. P. 4989(f). 



A single j)air of large supratemporal plates (^Fl. V, fig. 7, st.) overlaps the 

 occiput, exhibiting the same rugosity and sparse tubercalation as the hinder bones 

 of the cranial roof, and marked by the usual groove for the transverse slime-canal. 

 Each sii})ratemporal is wider than long and tapers towards the middle line of the 

 fish, where it meets its fellow of the opposite side. The comparatively small 

 exposed face of the post-temporal (PL V, fig. 7, pit.) is triangular in shape and 

 also tuberculated. Its inner face is smooth, and in the original of PL V, fig. 6,j>tL, 

 shows no feature beyond the articular facette for the supraclavicle ; but beneath 

 the same bone in B. M. no. P. 5591, there is a displaced long slender process which 

 seems to correspond with the internal descending process of the post-temporal in 

 Amid. Such a process has already been discovered by Mr. Alfred N. Leeds on a 

 post-temporal of Lepidotiis from the Oxford Clay of Peterborough. The supra- 

 clavicle is a deep and narrow plate of bone, only rugose at its upper end where it 

 is crossed obliquely by the slime-canal, and not serrated along its posterior edge. 

 The clavicle curves well forwards and its large expanded lower end is seen from 

 within below and just behind the mandible in PL VI. When the concave anterior 

 margin is exposed (as in the Sherborne School specimen), it is seen to be covered 

 with short oblique roAvs of small granulations. There are three large enamelled 

 post-clavicular plates, of which the upper two are shown in PL V, fig. 8, p)cl., and 

 in PL VI. They are smooth and exhibit a variable amount of serration of the 

 posterior edge in the lower portion. The upper postclavicidar is deep and narrow, 



