118 FOSSIL FISHES OF THE ENGLISH CHALK. 



Horizons and Localities. — Turonian zones : neighbourhood of Lewes. Zone of 

 Holaster planus : Cuxton, Kent. 



2. Osmeroides levis, A. S. Woodward. Plate XXIII, figs. 9—11. 



1895. Aulolepis typus, A. S. Woodward, Proc. Zool. Soc, 1894, p. 660 (in part), pi. xliii, figs. 2, 3, 5 



{error e). 

 1901. Osmeroides levis, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 15. 



Type. — Imperfect fish, probably from the zone of Holaster sulxjlobosus ; British 

 Museum. 



Specific Characters. - — A small species, attaining a length of about 20 cm. 

 Head with opercular apparatus occupying nearly one third of the length to the 

 base of the caudal fin. Length of cranium not exceeding twice its maximum 

 width at the occiput; each parietal bone not longer than broad; all external 

 bones remarkably smooth, the rugose markings being very coarse and feeble. 

 Position of dorsal fin as in the type species. 



Description of Specimens. — The type specimen (PI. XXIII, fig. 9) exhibits 

 nearly the whole length of the fish, though lacking the rostral part of the skull 

 and all the fins. Only two other specimens, also in the British Museum, are 

 known. 



The cranium is slightly shorter in proportion to its width than that of the type 

 species, and remarkable for the smooth and shining appearance of its external 

 bones, which are only feebly rugose or wrinkled. The supraoccipital (PI. XXIII, 

 fig. 10, socc.) does not appear to extend beneath the parietals so far forwards as 

 the frontal bones. The parietals (fig. 9, pa.) meet in a wavy suture and exhibit 

 a very sinuous margin ; they are not longer than broad. The squamosals (sq.), 

 which are crumpled so as to be marked with slight radiating ridges, extend further 

 forwards and flank the hinder part of the frontals. The frontals (figs. 9, 10, /V.) 

 are also radiately wrinkled behind, and bear traces of a finer rugosity on the 

 margin overhanging the orbit. They are smooth in their flattened middle portion, 

 and their median suture is strongly wavy behind while straight in the tapering- 

 front half of the bones. The longitudinal slime-canal is marked by a series of 

 pits just within the faintly rugose outer portion of each frontal. The mesethmoid 

 is relatively small, and seems to resemble that of the type species. On either 

 side of the anterior half of the frontal region, there is a relatively large supra- 

 orbital bone (fig. 10, spo.), which is smooth, but traversed by a large slime-canal. 

 The smooth postorbital cheek-plates (fig. 11, po.) are also relatively large, and 

 marked only by a few faint ridges which radiate backwards from the slime-canal 

 traversing their orbital border. 



The mandibular suspensorium is inclined as much forwards as in the type 



