﻿428 



ACTIN0PTEKYG1I. 



With regard to the arrangement of the genera of Palaeoniscidae, 

 it must be remarked that the scheme adopted below is merely a 

 provisional attempt to follow the lines of evolution. It may be 

 regarded as tolerably well established that (i.) the obliquity of the 

 suspcnsorium, (ii.) the loss of the baseosts in the median fins, (iii.) 

 the advanced position of the dorsal fin, and (iv.) the increasing 

 imbrication of the scales, are characters resulting from specializa- 

 tion. Ooccolepis, in which all these features are combined, thus 

 terminates the regular series. 



Synopis of Genera. 



A. Mandibular suspensorium nearly vertical ; 



scales rhomboidal. 



I. Fin-rays dichotomous ; caudal fin 



forked. 



Scales sculptured ; a continuous series 

 of enlarged ridge-scales; teeth 

 minute Canubius (p. 430). 



Scales smooth or in part faintly sculp- 

 tured ; teeth large, styliform, in 

 regular close series ; oral border 

 of maxilla straight Gonatodus (p. 434). 



As Gonatodus, but oral border of 

 maxilla sharply deflected at the 

 posterior expansion Drydenius (p. 437). 



Scales smooth, or in part faintly sculp- 

 tured ; teeth minute Amblypterus (p. 437). 



II. Fin-rays simple ; caudal fin obliquely 



truncated. 

 Scales sculptured, some flank-scales 

 very deep ; teeth minute ; fins 

 small, with fulcra Euryhpis (p. 448). 



B. Mandibular suspensorium oblique. 



I. Fin-rays dichotomous ; caudal fin 

 forked, 

 i. Dorsal fin remote, behind the anal. 

 Scales minute ; well - developed 



laniary teeth Cheirolepis (p. 451). 



ii. Dorsal fin remote, not extending 



behind the anal; laniary teeth 



well-developed. 



Trunk elongated ; anterior pectoral 



fin-rays articulated in distal 



third ; scales small, finely 



striated, deep and narrow on 



flank, with prominent inner keel. Nematoptychius (p. 457). 



