1 66 



TELEOSTOMES 



what seem to have been their primitive structural condi- 

 tions. Their skeleton has become highly calcified, its ele- 

 ments multiplying, fusing, and specializing. The notochord 

 has practically disappeared, owing to the complete formation 

 of bony vertebrae. The derm bones of the head, which in 



ANCESTRAL 

 TELEOSTOME 



(TABLE IV) 



PAUAE020IC 



PALAEONISCOID 



PALAEOZOIC 



CROSSOPTERVGIAN 



, MESOZOIC 



CATURID 



STURGEON 



LEPIDOSTEUS SILUROID 

 POLYPTERUS AMIA 



Fig. 171 A. 



UOPHOBRW4CH 

 ACANTHOPTERYGIAN 



The Phylogeny of the Teleostonies. 



SYNSNATM 



the ancestral Ganoid were at the surface, enamel-coated,* 

 are now deep-seated in the head, resembling true cartilage 

 bones ; their surfaces are usually deeply furrowed or ridged, 



* The enamel of Ganoid plates (ganoine) appears to be derived from the 

 underlying bony tissue, not deposited by the overlying epidermis (enamel 

 organ). 



