The Ganoids 247 
but in the more primitive types, or Ganoids, they may remain 
numerous, a reminiscence of the condition seen in the Crossop- 
terygians, and especially in Polypterus. Other variations may 
occur; the two coracoids 
sometimes are imperfect 
or specially modified, the 
upper sometimes without 
a foramen, and the ac- 
tinosts may be distorted 
in form or position. 
The Series Ganoidei.— 
Among the lower Actz- 
nopter’ many archaic 
traits still persist, and 
in its earlier representa- 
tives the group ap- 
proaches closely to the 
Crossopterygii, although 
no forms actually inter- 
mediate are known either 
living or fossil. The 
great group of Actinopteri 
may be divided into two 
series or subclasses, the 
Ganoidei, or Chrondrostet, 
containing those forms, 
mostly extinct, which re- 
tain archaic traits of one 
sort or another, and the 
Fic. 184.—Shoulder-girdle of a Flounder, Para- Teleostet, or bony fishes, 
lichthys californicus (Ayres). = 
in which most of the 
primitive characters have disappeared. Doubtless all of the 
Teleostei are descended from a ganoid ancestry. 
Even among the Ganoidei, as the term is here restricted, 
there remains a very great variety of form and structure. The 
fossil and existing forms do not form continuous series, but rep- 
resent the tips and remains of many diverging branches perhaps 
from some Crossopterygian central stock. The group constitutes 
at least three distinct orders and, as a whole, does not admit of 
i 
