LOPHIOSTOMUS. 155 
far forwards; their rays stout and ornamented. Scales rhombic and thick, with a 
wide overlapped border not produced at the angles, and the peg-and-socket 
articulation feeble or wanting; superficial ganoine more or less striated or pitted ; 
numerous series of narrow ventral scales. 
Type Species.—Lophiostomus divout, from the English Chalk. 
Remarks.—This genus is evidently related both to the Eugnathid and to the 
Amiide. Its thick rhombic scales and the presence of bony outgrowths on some 
of the external plates, considered together, suggest that it is one of the last 
members of the former family. The terminal forms of a group are often charac- 
terised by an armature of bony bosses or spines. 
1. Lophiostomus dixoni, Hgerton. Plate XXXII, figs. 4, 5. 
1852. Lophiostomus dixoni, P. de M. G. Egerton, loc. cit., n . 10, pls. x, x*. 
1888. Lophiostomus dixoni, A. 8. Woodward, Proc. Geol. Assoc., vol. x, p. 305. 
1895. Lophiostomus divoni, A. 8. Woodward, Catal. Foss. Fishes B. M., pt. 1, p. 359. 
Type. 
Head with part of abdominal region; British Museum. 
Specific Characters.—The type species, with skull attaining a length of 6 cm. 
External bones and fin-rays very conspicuously ornamented. Maximum width of 
cranial roof exceeding two thirds of its length; a pair of frontal prominences 
above the hinder part of the orbit, each laterally compressed and much elevated, 
the height exceeding half the distance between the pair; a similar pair of pro- 
minences on the squamosals. Gular plate as long as the tooth-bearing portion of the 
mandible, and at least two thirds as broad as long. Hinder border of scales with 
coarse, long, acuminate pectinations, continued on the outer face of the principal 
scales as oblique wrinkles or elongated pits. 
Description of Specimens—TVhe only satisfactory specimen of this species 
hitherto discovered is the type (Pl. XX XIII, fig. 4). All other specimens are 
mere fragments. 
All the external bones of the head and opercular apparatus are conspicuously 
ornamented with coarse and closely arranged tubercles of enamel, which are some- 
times elongated as on the preoperculum (fig. 4d), and sometimes fuse into 
vermiculating ridges as on the mandible, gular plate (fig. 4 ¢) and operculum. 
This ornament obscures the sutures in the cranial roof, which seems to have been 
slightly hollowed by a median longitudinal depression. The post-orbital portion 
of the cranium (fig. 4) 1s much broader than long, and bears two pairs of pro- 
minences, which are situated just above and behind the eyes (p.’) and at the squa- 
mosal angles (p.”) respectively. These prominences are laterally compressed, 
ornamented with the usual tubercles of enamel, and inclmed backwards (fig. 4 a, 
p»' p“). The frontal region (fr.) scarcely tapers forwards, but terminates shortly 
in advance of the orbits in a truncated border, which is excavated on either side 
