498 



FISHES 



CHAP. 



bodied Holosteaus with rhombic scales, rarely, as in Aelheolepis, 

 cycloid in the caudal region. All the fins possess fulcra. Teeth 

 more or less conical, with a tendency to become tritoral in certain 

 genera. Jugular plate present or absent. Acentrophorus (Upper 

 Permian) ; Semionotus (Trias of England, Germany, S. Africa, 

 and N. America) ; Lepidotus (Fig. 292) (Trias of Germany, 

 Jurassic of Europe and India, Cretaceous of Brazil) ; the deep- 

 bodied Dapedius (Lias of Dorset, Fig. 293), and Aetheolepis 

 (Jurassic of New South Wales) are characteristic genera. 



FIG. 293. Restoration of Dapedius politus. Lower Jurassic, Dorset, x . 

 (After Smith Woodward.) 



Fam. 2. Macrosemiidae. Closely related to the Semionotidae, 

 but with a more extended dorsal fin. Macrosemius (Upper 

 Jurassic of England, Germany, France); Notagogus (Upper Jurassic 

 of Naples, Bavaria, France) ; Petalopteryx (Upper Cretaceous of 

 Syria). 



Fam. 3. Pycnodontidae. Highly specialised deep - bodied 

 Fishes, with a small mouth and characteristic grinding or 

 tritoral teeth. Scales rhombic. Fulcra absent. Dorsal and 

 anal fins long. There is no jugular plate. The family ranges 

 from the Lower Lias to the Lower Eocene, inclusive. Mesodon, 

 Mesturus, Gyrodus, and Microdon are Jurassic genera. Coccodus 

 and Xenopholis occur in the Upper Cretaceous of Syria (Mount 

 Lebanon), and Pycnodus in various European Eocene formations. 



Fam. 4. Eugnathidae. Large - mouthed, elongate fusiform 



