24 The Ganoids 



For the group here called Lepidostei numerous other names 

 have been used corresponding wholly or in part. Rhombo- 

 ganoidea of Gill covers nearly the same groups; Holostei of 

 Miiller and Hyoganoidea of Gill include the Halecomorphi also; 

 Ginglymodi of Cope includes the garpikes only, while ALtheo- 

 spondyli of Woodward includes the Aspidorhynchida and the 

 garpikes. 



FIG. 14. Semionotus kapffi Fraas, restored. Family Semionotida. 

 (After Fraas, per Nicholson.) 



The Semionotida (Stylodontidcs) are robust-bodied Ganoids, 

 having the vertebrae developed as rings, the jaws with several 

 rows of teeth, those of the outer row styliform. 



Semionotus bergeri is a well-known species, with the body 

 moderately elongate. Semionotus agassizi and many other species 

 occur in the Triassic of the Connecticut valley and in New 

 Jersey. The body is very deep in the related genus Dapedium, 

 and the head is covered with strong bony plates. Dapedium 

 politum is a well-known species of the English Triassic. Tetra- 

 gonolepis (Pleurolepis] is a similar form, very deep and com- 

 pressed, with strong, firm scales. 



In the extinct family of Lepidotida the teeth are conical or 

 chisel-shaped, while blunt or molar teeth are on the inside of 

 the mouth, which is small, and the suspensorium of the mandible 

 is vertical or inclined forward. The body is robust-fusiform, 

 covered with rhomboid scales; the vertebrae form rings about 

 the notochord ; the teeth are either sharp or blunt. The dorsal 

 fin is short, with large fulcra. 



The best known of the numerous genera are Lepidotes, 

 rather elongate in body, with large, blunt teeth. Of the many 

 species of Lepidotes, Lepidotes elvensis abounds in the English 



