2() WEALDBN AND PURBECK FOSSIL FISHES. 



to delicate ridges concentric with the hinder and upper horders. The outer 

 face is also traversed by a slight longitudinal groove inclined forwards and down- 

 wards. The minute outer teeth, so far as preserved, are very slender, l)ut the 

 large smooth conical teeth of the spaced inner series are tumid at the base. 



Family Semionotid^.. 



Genus LEPIDOTUS, Agassiz. 



Lepidotes, L. Agassiz, Jahrb. f. Miii., G-eogii., etc., 1832, p. 145. 



Lepidotus, L. Agassiz, Poiss. Foss., vol. ii, pt. i, 1833, pp. 8, 233. 



Sphivrodas, L. Agassiz, torn, cit., pt. i, 18.)3, p. 15 (in part). 



Scrobodus, G. von Miinster, Neues Jahrl). f. Miu., etc., 1842, p. 38. 



Plesiodus, A. Wagner, Abli. k. bayer. Akad. Wiss., uiath.-phys. CI., vol. xi, 1863, p. 632. 



Prolepidohm, E,. Michael, Zeitsclir. deutsch. geol. Ges., vol. xlv, 1893, p. 729. 



Geveric ClKd-arlcr^. — Trunk fnsiform and onl}^ moderately compressed. 

 Marginal teeth robust, styliform ; inner teeth stouter, tritoral but smooth. 

 Opercular apparatus well developed, with a narrow arched preoperculum, but 

 with few branchiostegal rays and no gular plate. Ribs ossified. Fin-fulcra very 

 large and biserial, present on all the tins. Paired fins small or of moderate size; 

 dorsal and anal fins short and deep, the former just in advance of the latter 

 caudal tin slightly forked. Squamation regular and continuous, the scales 

 rhombic, very robust, smooth or feebly ornamented ; flank-scales not much deeper 

 than broad, with their wide overlapped margin produced forwards at the upper 

 and lower angles ; scales of dorsal and ventral aspect nearly as deep as broad ; 

 dorsal and ventral ridge-scales usually inconspicuous. 



Type Species. — Lcpiihjfiit^ rJrcusis (Ci/priiius elvevaia, H. D. de Blainville, Nouv. 

 Diet. d'Hist. Nat., vol. xxvii, 1818, p. 394; LepiJotiis (jujas, L. Agassiz, Poiss. 

 Foss., vol. ii, pt. i, 1838 — 37, pp. 8, 235, pis. xxviii, xxix) from the Upper Lias of 

 France, Wiirtemberg, Bavaria, and England. It is described in detail by F. A. 

 Quenstedt, " Ueber Lepidotus im Lias t" (Tiibingen, 1847) ; and the French type 

 specimen in the National Museum of" Natural History, Paris, is described and 

 figured l)y F. Priem, Annales de Paleontologie, vol. iii (1908), p. 5, pi. ii. A 

 closely related species, Lepidotus semiserratns^ Agassiz, is described by A. S, 

 Woodward, Proc. Yorks. Geol. and Polyt. Soc, n. s., vol. xiii, 1897, pp. 325 — 33G, 

 pis. xlvi — xlviii. 



On comparing the head of one of the earlier species of Lepidotus (Text-fig. 12) 

 with that of one of the latest (Text-fig. 13), it will be noticed that as the teeth 

 become stouter, the jaws are shortened and the mouth is relatively smaller. The 



