GANOIDEI. 367 



Oyrodus, Mesturus, Microdon, Cododus, Pycnodus, Mesodon, are 

 some of the genera distinguished by palaeontologists. (See 

 Kg. 102, p. 201.) 



SEVENTH SUB-ORDEE— LEPIDOSTEOIDEI. 



Scales ganoid, rhombic ; fins generally with fulcra; paired 

 Jins not loiate. Tree- and inter- operculum developed; generally 

 numerous Iranchiostegals, lut no gular plate. 



FiEST Family — Lepidosteid^. 



Scales ganoid, lozenge-shaped. Skeleton coinpletely ossified ; 

 vertebrcB convex in front and concave behind. Fins with fulcra ; 

 dorsal and anal composed of articulated rays only, placed far 

 backwards, close to the caudal. Abdominal part of the vertebral 

 column much longer than caudal. JBranchiostegals not numer- 

 ous, without enamelled surface. Heterocereal. 



Lepidosteus.^— Body elongate, sub-cylindrical ; snout elongate, 

 spatulate, or beak-shaped ; cleft of the mouth wide ; both jaws 

 and palate armed with bands of rasp-like teeth and series of 

 larger conical teeth. Four gills ; no spiracles ; three branchio- 

 stegals. Air-bladder cellular, communicating with the pharynx. 



'^ 

 Fig. 146. — Lepidosteus viridis. 



Fishes of this genus existed already in Tertiary times ; 

 their remains have been found in Europe as well as North 

 America. In our period they are limited to the temperate 

 parts of North America, Central America, and Cuba. Three 

 species can be distinguished which attain to a length of about 

 six feet. They feed on other fishes, and their general resem- 

 blance to a pike has given to them the vernacular names of 

 " Gar-Pike," or " Bony Pike." 



