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. 



139 



