154 FOSSIL FISHES OF THE ENGLISH CHALK. 
Description of Specimen.—This species is known only by the two pieces of one 
rostrum shown in Pl. XXXIII, figs. 3, 3a. The basal region is crushed and 
broken, displaying a very large central cavity, which becomes smaller forwards, 
and is then divided into two by the usual median partition; even in the 
terminal fragment, fig. 3 a, this double cavity persists as a pair of widely 
separated tubules. The fine tubercles clustered on the ridges which bound the 
median groove are pitted on the summit; and the peculiar nature of the ridged and 
pitted ornament of the greater part of the upper surface is illustrated in the 
enlarged fig. 3d. In the terminal part of the rostrum the median groove is 
only shghtly marked, and the longitudinal ridges of the ornament extend over it; 
these ridges are now very conspicuous, often subdivided into tubercles and in places 
reticulating. The lower surface (fig. 3a) is nearly smooth, but faintly impressed 
by a median longitudinal groove like that of the upper surface. 
Horizon and Locality.—Zone of Holaster subglobosus : Betchworth, Surrey. 
Family EKuGNaruip®. 
No typical member of this family has hitherto been found in the Chalk; for 
the fragment of jaw from the Chalk of Lewes named Caturus similis by Agassiz 
(Poiss. Foss., vol. 1, pt. n, 1844, p. 118, pl. Ixvi a, fig. 9) is indeterminable and 
probably belongs to a Teleostean fish. Two genera, however, Lophiostomus and 
Neorhombolepis, from the Enghsh Chalk, appear to be highly specialised Eugna- 
thidz, with completed vertebral centra, and without fulcra on the paired fins. 
Genus LOPHIOSTOMUS, Egerton. 
Lophiostomus, P. de M. G. Egerton, Figs. and Descript. Brit. Organic Remains, dec. vi (Mem. Geol. 
Surv., 1852), no. 10. 
Generic Characters.—Head relatively large, with very wide gape, and apparently 
much depressed. External head-bones and the opercular bones stout, more or less 
ornamented with tubercles and rugze of enamel; also sometimes bearing prominent 
bosses, notably in one or more pairs on the cranial roof. Maxilla with a straight 
or shghtly concave tooth-bearig border, and the premaxille fused together, pro- 
bably also with the ethmoid; teeth conical, in regular series, large and hollow on 
the margin of the jaw, mmute on the inner bones, not in sockets. Suboperculum 
nearly half as large as the operculum, which is quadrangular, but truncated at the 
postero-superior angle; gular plate very large. Vertebral centra apparently 
ring-shaped. Paired fins without fulera, and the pelvic pair relatively small and 
