122 



WEALDEN AND PURBECK FOSSIL FISHES. 



Generic Characters. — Head large and teeth minute; sclerotic ossified. Maxilla 

 arched, with a slightly convex tooth-bearing border; mandible prominent, and 

 dentary rising sharply into a thickened, obtuse elevation near its anterior end ; 

 preoperculum broad mesially, with a large inferior limb, marked with radiating 

 ridges; suboperculum large, but smaller than the trapezoidal operculum, from 

 which it is divided by an oblique suture. Vertebral centra in the form of much- 

 constricted cylinders, with little or no secondary ossification. Pelvic fins relatively 

 large; dorsal fin about as long as deep, opposed to the pelvic pair or to the 

 space between the latter and the anal ; anal fin small, not much extended ; caudal 

 fin deeply forked. Scales completely covering^he trunk ; no enlarged or thickened 

 ridge-scales. 



Type Species. — Leptolepis bronni (L. Agassiz, Poiss. Foss., vol. ii, pt. i, 1888, 



*s«3S? 



Fio. 37. — Leptolepis dubius (Blainville) ; restoration of skeleton, scales omitted, reduced in size. — Lower 

 Kimmeridgian (Lithographic Stone) ; Bavaria. From British Museum Catalogue of Fossil Fishes. 



p. 13; pt. ii, 1844, pp. 133, 294), from the Upper Lias of AViirtemberg, Bavaria, 

 France, and England. 



Remarks. — The most characteristic bone of Leptolepis is the dentary of the 

 mandible (PI. XXIII, fig. 7). The genus has a very wide distribution both in time 

 and space, ranging from the Upper Lias to the Lower Cretaceous in Europe, and 

 from Spitzbergen in the north to Australia in the south. The later species as a 

 rule (e. g. Leptolepis dubius. Text-fig. 37) exhibit more secondary ossification in 

 the vertebrae than the earlier species ; but a Kimmeridgian form from King Charles 

 Land (L. nathorsti, A. S. Woodward, Bihang K. Svensk. Vet.-Akad. Handl., 

 vol. xxv, sect, iv, no. 5, 1900, p. 4, figs. 2—11) and the Purbeckian species 

 described below seem to have primitive vertebral centra like those of L. bronni. 



1. Leptolepis brodiei, Agassiz. Plate XXIII, figs. 1 — 6. 



1845. Leptolepis brodiei, L. Agassiz, in P. B. Brodie, Foss. Insects, p. 15, pi. i, figs. 1, ::. 

 1845. Leptolepis nanus, P. M. G. Egerton, in P. B. Brodie, op. cit., p. 15, pi. i, fig. 5. 



