42 WEALDEN AND PURBECK FOSSIL FISHES. 



(PL IX, fio-. 1, mx.). Its outer face is smooth, and teeth have not been observed 

 on the oral border in the known specimens. A small narrow supramaxilla, 

 pointed behind, occurs above its hinder expansion (.s/».t.). The premaxill^ are 

 known only in the small specimen shown in PI. X, figs. 3, o a, pnx., where they 

 are shaped nearly as in Lepidotus minor (seep. 30). The broad anterior ascending- 

 process of each bone clearly passes up beneath the anterior end of the frontal ; 

 and the comparatively small portion extended along the oral border bears a row 

 of styliform teeth, each capped by enamel. The mandible is short and stout, 

 much deepened in the coronoid region, much horizontally expanded at the 

 symphysis. As seen from the outer face (PI. IX, fig. 1, (uj.), the angular bone is 

 especially short and deep, smooth above but more or less coarsely rugose below, 

 above the longitudinal groove for the passage of the slime-canal. It is capped by 

 a very small coronoid bone (B. M. no. P. 6342). The hinder ascending part of the 

 dentary (J.) is as deep as the angular and coronoid bones together, and its outer 

 convex face is either smooth or faintly rugose. Just in front of this ascending 

 part the bone is of least depth, and it then deepens slightly again towards the 

 symphysis (PI. VIII, fig. 2h), which slopes sharply backwards, sometimes 

 approaching a horizontal plane for the support of the massive splenial. The oral 

 border in front bears a single row of six to nine comparatively small but stout 

 styliform teeth (PI. XI, fig. 6) ; and the outer face of the bone is more or less 

 coarsely rugose, with the course of the slime-canal marked by a row of large pits. 

 The tooth-bearing end of a very small dentary has already been described under 

 the name of T/'tragouolepis mastodontens by L. Agassiz, Poiss. Foss., vol. ii., pt. i 

 (1837), p. 216, pi. xxiiic% figs. 3, 4. The massive splenial (PI. XI, fig. 5, spl.) 

 meets its fellow in an extensive symphysis, and its slightly concave oral face is 

 covered by five or six rows of tritoral teeth, which are largest within. There is 

 some ossification in the meckelian cartilage, but its shape and extent are 

 uncertain. 



All the teeth are fused Avitli the supporting bone, not in sockets, and they 

 have a large pulp-cavity, from which very minute, irregularly branching tubuli 

 radiate into the dentine. Successional teeth are abundant in the thick cancellated 

 bone beneath the functional teeth (PI. XI, fig. 1), and they clearly turn through 

 an angle of 180° in the course of development as in other species of Lepidofnx 

 (PI. XI, figs. 1, r] h, bh). The enamelled crown, when unworn, rises to a sharp 

 median apex ; and occasionally, as in the hinder teeth of PI. XI, fig. 2, there is a 

 slight apical constriction which tends to make it mammilliform (fig. 2 c). Even in 

 the type specimen of Lepidotus fittoni (contrary to the statement by Agassiz) some 

 of the inner teeth exhibit the median apex. When Avorn they become first rounded, 

 then flattened, and eventually sometimes have the pulp-cavity exposed ; but there 

 is no uniformity in the degree of wear in any group of teeth, and they appear to 

 be shed in indefinite order. In all undoubted specimens of L. mantelli the enamel 



