CHAPTER XXI 



TELEOSTEI : GENERAL CHARACTERS MALACOPTERYGII 



OSTARIOPHYSI 



Order IV. Teleostei.^ 



As stated above (p. 495), the Holostean Ganoids pass very 

 gradually into the Teleosteaus, the lower groups of which appear 

 to have been directly derived from them. The precise defini- 

 tion of the Order Teleostei, as compared with the Ganoid Order 

 Holostei, is a matter of some difficulty. The most important 

 character appears to be the presence of an ossified supraoccipital 

 bone.^ Eemnants of primitive characters, such as ganoid scales, 

 fulcra, rudiments of a splenial bone, spiral valve to the intes- 

 tine, multivalvular conus arteriosus, are still found in some 

 lower Teleosteans, but no longer in that combination which 

 serves to define the preceding order. Although Albula is excep- 

 tional among all Teleosteans in having two transverse series of 

 valves to the bulbus arteriosus instead of one, no Ganoid has 

 fewer than three. 



The first remains of Teleosteans appear scantily in the Upper 

 Trias, and it is not before we reach the Upper Cretaceous that 

 they assume preponderance over other Teleostomes ; whilst in 

 the Upper Eocene they have already attained a development 

 and variety of types comparable to their present condition. Out of 

 some 12,000 well-established species of Fishes known to exist at 



' The natural position of the Teleostei in the series of Fishes is indicated on 

 p. 149. 



' This exists in Dapedius, as pointed out by A. S. Woodward. But this genus 

 should certainly be removed from the -vicimty of Zepidotus, and it seems to bear 

 affinity with the Pholidophoridae. 



541 



