LEPIDOTUS. 20 



The chondrocranium is unknown, but it must have been imperfectly ossified, 

 and, as sliown by specimens in the British Museum (PI. V, fig. 6) and the Warwick 

 Museum, the membrane bones of the roof were readily detachable from it. The 

 parietal bones (PI. V, figs. 6, 7, pa.) form a nearly symmetrical pair united in a 

 slightly Avavy median suture ; and that of one side extends a little further forwards 

 on the cranial roof than that of the other side. Each bone is about one and a half 

 times as long as broad, and its outer face is not only rugose, but also coarsely 

 and irregularly tuberculated, and marked in the middle by a short transverse 

 groove for the slime-canal. The squamosal on each side is a longer and narrower 

 bone, united in a slightly wavy suture with the parietal, extending from the 

 occiput behind to the postorl)ital prominence of the frontal forwards. Its outer 

 face (Pl.V, figs. 7, 8, sq.) is also rugose and coarsely tuberculated, while its inner face 

 (PI. V, fig. 6, sq.) bears the usual elongated articular facette for the upper end of 

 the hyomandibular. The frontals (PI. V, figs. 6 — 8,//-.) are at least two and a 

 half times as long as the parietals, and are also united in a slightly wavy median 

 suture. Each is widest behind, the maximum width being about a quarter of the 

 total length ; and its comparatively narrow anterior portion ends in a few pointed 

 digitations. Its outer margin is regularly excavated for the relatively large orbit, 

 thus producing definite postorbital and preorbital prominences. Its outer face is 

 coarsely and irregularly tuberculated as far forwards as the middle of the orbit, 

 while the anterior portion is marked only with a few irregular longitudinal 

 grooves. The longitudinal slime-canal, which opens on the outer face in rather 

 large pores, is enclosed by bone which forms a rounded ridge on the inner face 

 (PI. V, fig. 6, fr.). The ethmoid region and. the nasals remain unknown. The 

 parasphenoid (PI. V, fig. 9) which is commonly ascribed to this species but has 

 not yet been definitely seen in position, closely resembles that of Lepldofus Inti- 

 fvons.'^ It is narrowest at the small digitate basipterygoid processes, expanding 

 much behind and exhibiting a deep cleft in its hinder margin. It is pierced 

 between the basipterygoid processes by a foramen for the passage of the intei'nal 

 carotids, and it is toothless. 



The cheek is completely covered with plates, which form a circumorbital ring, 

 bounded behind by postorbitals and continued in front by a few preorbitals. All 

 are irregularly tuberculated, while the circumorbitals behind and below the orl)it, 

 as well as the preorbitals, are also marked by the usual slime-canal. Of the circum- 

 orbital ring, four plates occur above the eye, occupying the excavation in the 

 frontal border between the preorbital and postorbital prominences and extending 

 backwards to bound the anterior end of the squamosal (see PI. V, figs. 7, 8). 

 These plates are variable in shape, but the foremost is usually the longest. The 

 two posterior circumorbitals are comparatively small and narrow, while the lower 



1 A. S. Woodward, ' On the Cranial Osteology of the Mesozoic Ganoid Fishes, Lepidotus and 

 Dapedivs.' Proc. Zool. Soc, 1893, p. 561, text-fig. 3. 



