VII 

 THE TELEOSTOMES 



All fishes not to be grouped among Sharks, Chimae- 

 roids or Lung-fishes, have been included in the fourth 

 sub-class, Teleostomi. In this are to be merged the two 

 time-honoured groups, Ganoids* and Teleosts, since it is 

 now found that there are absolutely no structures of the 

 one group that are not possessed by members of the other. 

 The terms, therefore, '* Ganoid " and "Teleost," must 

 be used in a popular and convenient, rather than in an 

 accurate sense; the former to denote the "old-fashioned" 

 Teleostome, with its rhombic bony body plates, and carti- 

 laginous endoskeleton ; the latter, the modern ''bony fish," 

 with rounded, horn-like scales and its calcified endo- 

 skeleton. 



Teleostomes present so wide a range of variation that 

 it becomes exceedingly difficult to include in a single 

 definition their minor structural characters. 



As a basis for the comparison of the Teleostomes, the 

 characteristic structures of a single type, e.g. the Perch, 

 might conveniently be taken. From these conditions, 

 typical of a modern and highly specialized form, the simple 

 structures of the ancient, more primitive, and ancestral 

 Ganoids may afterward be readily understood. 



* The term Ganoid, as here used (as far as p. 147), includes the Crossopte- 

 rygians as well. 



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