324 



ORDERS OF FISHES. 



families Dapedida, Lepidotida, and Leptolepidce. In the Dapedi- 

 d<z (fig. 284, i), the tail-fin is only slightly heterocercal, and the 



Fig. 284. i. Dapedius tetragonolepis. 2. Leptolepis sprattiformis. 

 3. Lepidotus Valdensis. 



back teeth are obtuse. Dapedius itself is compressed and deep- 

 bodied, and is exclusively confined to the Lias. The front-teeth 

 in this genus are notched or bifurcate. ^Echmodus is also 



Fig. 285. Tetragonolepis (restored). Lias. 



exclusively Liassic ; but Semionotus and Pholidophorus range 

 upwards to the Chalk or to the highest Oolitic strata. The 

 Oolitic genus Tetragonolepis (fig. 285) is closely similar to Da- 



