The Ganoids 



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 Acti- 

 nopteri 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 Chrondrostei, 

 containing those forms, 

 mostly extinct, which re- 

 tain archaic traits of one 

 sort or another, and the 

 Teleostei, or bony fishes, 

 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 

 a.t least three distinct orders and, as a whole, does not admit of 



FIG. 1. Shoulder-girdle of a Flounder, Para- 

 lichthys californicus (Ay res). 



