46 WEALDEN AND PURBECK FOSSIL FISHES. 



Dawson (Fl. VIE, fig. 7), where they are equally elevated, their greatest height 

 measuring about two-thirds of the depth of the trunk at the insertion of the dorsal. 

 The enamelled biserial fulcra of the dorsal fin are comparatively large, and four or 

 even five (B. M. no. P. 6336) of these fulcra, of gradually increasing length, are 

 directly inserted in the ridge of the l)ack. The dorsal fin-rays, about fourteen in 

 number, decrease in length backwards, and each is very finely divided and 

 articulated for more than half of its length. The anal fin is closely similar to the 

 dorsal, but with smaller biserial fulcra, only about ten rays, and the undivided 

 bases of these rays relatively short. The caudal finis known only by its basal part, 

 which resembles that in other species (PI. VII, fig. 7). 



All the scales are usually smooth, sometimes with a faintly concave face, but 

 there is a tendency to coarse oblique grooving, especially when the enamel is partly 

 removed and the subjacent structure which causes this grooving becomes evident 

 (PI. VIII, fig. 4). Irregularly tuberculated or rugose scales have only been 

 observed in the anterior dorsal region of one small specimen (PI. IX). The scales 

 on the anterior part of the abdominal region, especially on the flank (PI. XI, fig. 7), 

 are usually finely serrated, but the degree of serration varies considerably from 

 the extreme in the original of PI. IX, through the apparently partial serration in 

 the type specimen (PI. VIII, fig. 1), to the more irregular serration in the so-called 

 L. fittoni (PI. VlIT, fig. 2). In the scales of other parts the hinder margin is 

 smooth. As counted along the lateral line, the total numl^ei' of transverse series 

 of scales is about forty, while the number in a series above the origin of the pelvic 

 fin is nineteen or twenty. The principal flank-scales in the abdominal region are 

 somewhat deeper than l)road, and those of the lateral line, in the eleventh or 

 twelfth row above the pelvic fins (PI. IX, fig. 1 , I.), are notched just above their 

 postero-inferior angle and usually pierced by an oval foramen near their anterior 

 margin. The scales more dorsally and ventrally, and in the caudal region, are 

 nearly equilateral or even broader than deep ; and many of those in the dorsal 

 region between the occiput and the dorsal fin are pierced by a large foramen for 

 the exit of slime-apparatus, without any definite arrangement in lines (PI. VII, 

 fig. 7; PI. VIII, figs. 2 (/, 3). Beneath the base of the dorsal and anal fins the 

 scales become small and irregular, with rounded angles, and with enamel often 

 failing to extend to the edge. At the base of the caudal fin the scales are also 

 small and irregular, but rather elongate-rliomboidal in shape. The dorsal ridge- 

 scales are not much, if at all, enlarged ; but most of them are acuminate, and they 

 vary much in shape fi*om the slight prominence seen in PI. VIII, fig. 3, to the 

 extreme acumination made conspicuous by crushing in the original of PL VII, 

 fig. 7. The ventral ridge-scales are neither enlarged nor more acuminate than the 

 other scales ; the usual enlarged scales occur near the origin of the anal fin. 



All the scales are thick, and those oF the abdominal region are united in the 

 usual manner by deep overlap and a peg-and-socket articulation (PI. XI, figs. 7, 8). 



