84 FOSSIL FISHES OF THE ENGLISH CHALK. 



Some of the principal characters of the species are illustrated in Pis. XVIII, 

 XIX. The head (PL XIX, fig. 2) appears to be closely similar to that of G. radians, 

 with indications of a well-developed slime-canal system. The jaws are of the 

 same shape, with corresponding supramaxillse (smx. 1,2); but the teeth of the upper 

 jaw arc relatively larger and perhaps blunter than in the species alread} r described. 

 The right premaxilla, with its characteristic dentition, is shown of thrice the natural 

 size in PI. XIX, fig. 2 a. The preoperculum, somewhat abraded and broken in the 

 original of PI. XIX, fig. 2 {pop), is also nearly similar to that of G. radian* ; but 

 the operculum, of which fragments remain in the originals of PI. XVIII, fig. G, 

 PI. XIX, fig. 2 (op.), differs in being for the most part smooth and covered with 

 thin, pectinated scales. The vertebral centra are as small as in G. radians, and the 

 ribs (PI. XIX, fig. 1, r.) are clearly stout and long. 



The supraclavicle (PL XIX, fig. 2, scl.) is deep and smooth, while the clavicle, 

 imperfectly exposed in PL XIX, fig. 2 (cl.), has the usual proportions. The 

 pectoral fin, shown turned downwards and forwards in the same figure (pet.) is 

 small and delicate, with about 10 rays. The pelvic fins (PL XVIII, figs. G, 7, 

 ph. ; PL XIX, fig. 1, plv.) arise immediately behind the pectorals on the inferior 

 flattened face of the body. When seen from below (PL XVIII, fig. 7), their bases 

 are observed to be separated by a large, median, ovoid scale. Each consists of 

 about 9 rays, which are shown to be very stout when the fin is spread (PL XIX, 

 fig. l,plv.). The rays are divided and articulated distally, where they are thus 

 usually imperfect in the fossils; but the original of PL XIX, fig. 1, seems to show 

 that they were not so excessively elongated as in G. radians, the fin, when ad- 

 pressed to the trunk, not reaching the anal fin. The depth and extent of the 

 dorsal fin (PL XVIII, fig. G, do.; PL XIX, fig. 1, do.) are not quite clear; but it 

 arises opposite a point just behind the insertion of the pelvic fins, and it must have 

 occupied nearly, if not quite, half the length of the back. Its rays are very stout, 

 articulated and divided distally. The anal fin (PL XVIII, fig. G, a; PL XIX, 

 fig. 1, a) consists of equally stout rays, which are also much elongated and divided 

 and articulated distally. This fin seems to have been deeper than long, 

 with about 10 rays, which would nearly reach the base of the caudal fin if they 

 were adpressed to the trunk. The long base of the foremost anal fin-rays bears a 

 fine rugose ornament. The caudal fin (PL XVIII, fig. G, c.) is deeply forked, and 

 its rays arc closely articulated and divided beyond a very short base. 



The scales are so large that there are only nine in each transverse series on the 

 flank, 1 he lowermost being bent in the usual manner to enter both the flank and 

 the flattened ventral face. This narrow face (PL XVIII, fig. 7) is completely 

 covered by the half-scales <>f each side with only one median longitudinal row of 

 the ordinary scales. The principal flank-scales (PL XVIII, fig. 9) are nearly twice 

 ;is deep as broad, and their exposed area is more than twice as deep as broad. 

 Their binder border is coarsely and strongly pectinated, Gut the rest of their outer 



