144 



TELEOSTOMES 



Such in outline are 

 the essential structures 

 of a Teleost. They may 

 now be briefly con- 

 trasted with the more 

 important characters of 

 the Ganoids. 



In skeletal structures 

 the Perch (Fig. 146) 

 may be strikingly con- 

 trasted with the most 

 nearly ancestral form 

 of Ganoid (Fig. 147). 

 In this, Polypterus (p. 

 148), the skeleton re- 

 tains a semi-calcified 

 condition. Its verte- 

 bral centra are practi- 

 cally separate from the 

 arches ; its ribs, R, are 

 equivalent to the trans- 

 verse processes ; its ac- 

 cessory ribs, AR, to 

 the '*ribs"of Teleosts. 

 The cartilaginous brain 

 case is notably re- 

 tained; the membrane, 

 or dermal bones, of the 

 head roof, as Fy P, SP, 

 POy O, are clearly 

 scale -like, with an 

 enamelled surface, sim- 

 ilar in character to 



