AMIOIDEI 



333 



or with rounded hinder edge ; they are small or absent. As a rule, 

 there are no distinct vertebral bodies. The pectoral and caudal fins are 

 very large, and the hypochordal lobe is supported by a much-expanded 

 haemal arch. The pelvics are small and far forwards. 



Euthynotus, Wagner ; Sauropsis, Ag. ; Asthenocormus, A. S. W. j 

 Pachycormus, Ag. ; Hypsocormus, Wagner (Fig. 310) ; Jurassic / Europe. 

 Protosphyraena, Leidy ; Cretaceous, Europe and North America. 



Family AMIIDAE. These fish differ from those of the previous family 

 chiefly in external shape. The body is fusiform, the dorsal and anal fins 



FIG.. 312. 



Head of Amia ccdva, L. ; oblique ventral view, e, eye ; /, pectoral fin ; g, median gular 

 plate ; Lg, lateral gulars or branchiostegal rays ; l.j, lower jaw ; ?)i,[mouth ; n, nostril ; oj>, 

 operculum ; s.a, serrated appendage. 



become lengthened, and the caudal, which is little if at. all forked, shows 

 no external sign of heterocercy. Fulcra, small on the median, are absent 

 from the paired fins. The scales are thin, squarish, and deeply over- 

 lapping. The ganoine is represented in Amia only by the surface orna- 

 mentation on the scales, and this genus has lost all fulcra [508]. There 

 are vestigial cheek - bones, but a large median gular remains. Amia 

 has a special serrated bony plate projecting into the branchial chamber 

 (Fig. 312). The hypo- and pleurocentra form complete alternating 

 rings in the caudal region (Fig. 311). In Liodesmus the notochord was- 

 persistent. 



