428 
ACTIN0PTERYG1I. 
With regard to the arrangement of the genera of Paheoniscidse, 
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 
suspensorium, (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. Coccolepis , 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 . 
Scales smooth or in part faintly sculp¬ 
tured ; teeth large, styliform, in 
regular close series; oral border 
of maxilla straight. 
As Gonatodus , but oral border of 
maxilla sharply deflected at the 
posterior expansion. 
Scales smooth, or in part faintly sculp¬ 
tured ; teeth minute, r. 
II. Fin-rays simple ; caudal fin obliquely 
truncated. 
Scales sculptured, some flank-scales 
very deep ; teeth minute; fins 
small, with fulcra . 
B. Mandibular suspensorium oblique. 
I. Fin-ravs dichotomous; caudal fin 
forked. 
i. Dorsal fin remote, behind the anal. 
Scales minute ; well - developed 
laniary teeth. 
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. 
Canobius (p. 430). 
Gonatodus (p. 434). 
Drydenius (p. 437). 
Amblypterus (p. 437). 
JEuryhpis (p. 448). 
Cheirolepis (p. 451). 
Nematoptychius (p. 457). 
