82 



PISCES 



tion in the middle of the crown. Scales marked with more or less parallel 

 ridges, ending in denticulations at the hinder border. Common in the 

 Muschelkalk and Lettenkohle. 



The generic names Nephrotus, Cenchrodus, Omphalodus, Ilemilopas, Meyer, 

 and Sargodon, Plieninger (Fig. 146), are applied to rounded 

 or chisel-shaped teeth from, the Trias and Rhaetic. 



Lepidohis, Ag. (Sjjhaerodics, p.p. Ag. ; Plesiodus, Wagner ; 

 Prolepidotus, Michael), (Figs. 147, 148). Trunk fusiform and 

 only moderately compressed, covered with thick, smooth, or 

 obliquely striated scales, which are deeply imbricating and 

 have the angles of the overlapped border more or less 

 produced. Head and opercular bones more or less enamelled, 

 smooth or tuberculated. Teeth hemispherical to obtusely 

 conical. Successional teeth numerous, the incipient germ lying exactly in 

 the opposite direction to that of the functional tooth, thus making a revolution 

 of 180° while the root of the old tooth is absorbed and it prepares to appear 



Fig. 140. 



Sargodon tomicus. 

 Plien. Rhaetic ; Kem 

 iiatli, AVtirtemberg. 



■M^f¥':$kp^f, 



Lepidotus notoptcras, Ac 



Fig. 1-17. 

 Upper Jurassic Lithographic Stone) ; Soleuliofeii. 1/5 nat. size. 



(Fig. 148, A). Fin fulcra very large and biserial (Fig. 148, I)), present on all 

 the fins. Pectoral fins large ; pelvic fins small ; large dorsal fin opposed to 

 the pelvic pair; caudal fin more or less forked. Ranging from the Keuper 



Fig. 14S. 

 Lepidotus. A, Fragiiient of jaw with successional teeth. B, Tooth in side view and from above. C, Scale. 

 D, Fulcral annatiire of dorsal tin. /, Fulcra ; x, Unpaired dorsal -scale ; y, First basal scale of dorsal fin ; s, z', 

 lateral scales. Xat. size. 



to the Lower Cretaceous, some of the later species having the largest, stoutest 

 teeth and well-developed ring-vertebrae. The type species, L. elvensis, Blv. 

 sp., common in the Upper Lias of Wiirtemberg, Bavaria, France, and England. 

 L. maximus, AYagn., L. notopterus, Ag. (Fig. 147), and other species well pre- 



