OSMEROIDES. 119 



species. The premaxilla considerably underlaps the tapering front end of the 

 maxilla (fig. 11, mx.), which is much arched, and bears only one longitudinal ridge 

 close to its oral margin. The supramaxillae are of the characteristic shape, 

 relatively large, and marked only by a few short longitudinal ridges. Both the 

 premaxilla and maxilla are seen to bear minute clustered teeth. The mandible 

 (fig. 11) tapers gradually forwards from the rounded coronoid elevation to the 

 blunt symphysis, and its post-coronoid region is very short. Its outer face is 

 smooth, except near the lower border, where there are two longitudinal ridges, the 

 lowermost pierced by a series of openings of the slime-canal. The dentary bone 

 (<1.) bears a cluster of minute teeth, which widens and spreads outwards at the 

 symphysis; the articulo-angular {<ig.) contracts to a very narrow bar below its 

 articular facette. 



The bones of the opercular apparatus (PI. XXIII, fig. 11) exhibit only feeble 

 traces of the ornament which is characteristic of the type species. The operculum 

 (op.) is trapezoidal in shape, about three quarters as broad as deep. The sub- 

 operculum (sop.) exhibits a very large ascending process at its antero-superior 

 angle. The interoperculum (top.) is almost covered by the expanded lower end 

 of the preoperculum (p>op.). The upper branchiostegal rays (br.) are broad and 

 nearly smooth. The gular plate (git.) is very large and also smooth. 



The vertebras have been only imperfectly observed, but appear to resemble 

 those of the type species. The hamial arches are stout and expanded at the base 

 of the caudal fin. 



In the pectoral arch, the smooth, long post-temporal bones (PL XXIII, fig. 10, 

 ptt.) curve slightly to their pointed anterior end, which impinges on the occipital 

 border. The supraclavicle is rather long, and exhibits only the feeblest wrinkling 

 on its outer surface. Of the fins, only parts of the undivided bases of the 

 pectorals and dorsal are known. The distance between the origin of the dorsal 

 fin (fig. 9, do.) and the occiput considerably exceeds the length of the head with 

 opercular apparatus. 



The scales closely resemble those of the type species, but the concentric ridges 

 on their exposed portion appear to be generally more conspicuous, while there is 

 no trace of fine radiating ornament. When the minute granulation is removed 

 from the covered portion of the scales, the few radiating grooves here are con- 

 spicuous. The lateral line produces the usual smooth ridge. 



Horizon and Localities. — Zone of Holaster subglobosus ; Burham, Kent; Lewes, 

 Sussex. 



3. Osmeroides latifrons, sp. no v. Plate XXIV, figs. 1 — 3. 



Type. — Skull, etc., from zone of Holaster subglobosus ; British Museum. 

 Specific Characters. — An imperfectly known species, about as large as the 



