FISHES. 



277 



fossil genera. To this family belong the large flat teeth 

 (Acrodus nobilis) met with in the lias. 



4th Family. The HYBODID^;, the type of which is Hylo- 

 dusj an extinct genus, allied to the sharks, with conical, 

 but not compressed, teeth. The genera are distributed in 

 the different stages from the carboniferous to the neocomian. 



5th Family. The SQUALID^E, have for their type the 



FIG. 1SS. Tooth of the Fossil Genus, Otodus. 



Syualus, or shark, of our seas. Characterised by their 

 elongated body, adapted for rapid motions, by their sharp, 

 triangular, lancet-shaped teeth. Twenty fossil genera have 

 been identified. Figs. 188 and 189 show the forms of the 

 teeth in Otodus and Lamna. 



6th Family. The CHIM^BID^E, have for their type the 

 Chimcera of our seas. The fossil genera commence in the 

 oolitic, but are most abundant in the tertiarv strata. JN"one 



