LEPTOTRACHELUS. 7:; 



Owing to the nature of the chalky matrix in which the fossils of this species 

 occur, they can only bo cleaned and prepared with difficulty, and the dermal 

 armour is nearly always much damaged or destroyed. The characteristic scutes 

 are best displayed in the type specimen (figs. 1, la, lc) ; but even in this remark- 

 able fossil their arrangement can only be understood by reference to the well-pre- 

 served fishes of allied species from the Cretaceous of Sahel Alma, Mount Lebanon 

 (described in ' Catal. Foss. Fishes B. M.,' pt. iv, 1901, pp. 174 — 184). The armour 

 clearly begins immediately behind the head and extends along the whole length of 

 the trunk to the base of the caudal fin (B. M. no. 43512). The wide angle between 

 the right and left halves of each dorso-lateral and ventro-lateral scute indicates t hat 

 the body was rounded, not much laterally compressed. The paired dorso-lateral 

 and ventro-lateral rows are apparently similar and consist of triradiate scutes (fig. 

 lc, d., v.), which scarcely overlap. Their anteriorly directed arm is longest and 

 acutely pointed. Their backwardly inclined arms diverge at a considerable angle, 

 and the longer of the two is truncated distally to meet its fellow of the opposite 

 side at the middle line of the body, while the shorter arm has a more tapering or 

 rounded end. The outer face of each scute is strengthened by a thickening of the 

 hinder border and by a longitudinal median ridge, which bears a recurved, uncinate 

 spine throughout the posterior abdominal and caudal region : it is also sometimes 

 marked with a few short radiating lines and tubercles. One specimen (fig. 8) shows 

 a gradual enlargement of the three ventro-lateral scutes just in advance of the 

 pelvic fin, and the anterior abdominal scutes seem to be narrower than those 

 further back ; but otherwise there is little variation in size in any part of the series. 

 The scutes of the lateral line, as seen on the anterior abdominal region, are narrow 

 and almost heart-shaped, with their two hinder arms diverging at a very acute 

 angle (fig. 1 c, I.) ; and some of them are clearly tuberculated. It seems likely, 

 however, that towards the middle of the body they become more distinctly t ri- 

 radiate, as in Leptotrachelus triqueter (see B. M. no. P. 4863) ; for a detached scute 

 of the lateral line in Dr. G. J. Hinde's Collection, probably referable to L. elongatus, 

 has widely divergent posterior anus. This scute (figured in Proc. Geol. Assoc, 

 vol. x, pi. i, fig. 7) bears a prominent recurved spine above the tube for the slime- 

 canal, and its hinder border is faintly and coarsely serrated. On the thinks of the 

 caudal region there are sometimes traces of very thin and smooth Lath-shaped 

 plates, which were probably connected with the free arms of the scutes of the 

 dorso-lateral and ventro-lateral series, as in the Lebanon species. 



Remarks. — Worm-burrows Lined with miscellaneous scales and other fish- 

 remains are not uncommon in the Chalk, and portions of these were erroneously 

 assigned to //. elongatus by Agassi/,, loc. cit., p. 259, pi. Lxvia, figs. A \>. They were 

 originally described under the name of Muraena? lewesiensis by Mantell, 'Foss. 

 South Downs' (1822), p. 232, pi. xxxiv, tig. LI; pi. xl, tig. A Their true nature 

 was firs I demonstral *d by W. Davies, G-eol. Mag. [2], vol. vi (1879), p. 1 IA Similar 



lo 



