528 FISHES. 



The relationships of Fishes. 



Balfour regarded the Elasmobranchs as nearest the ancestral stock ; 

 while from hypothetical Proto-Ganoids he derived on the one hand the 

 Dipnoi, on the other hand the Ganoids, and thence the Teleosteans. 



But it must be noted that the Dipnoi are markedly separated in many 

 ways from living Ganoids. Moreover, the extinct Ganoids form a very 

 large and diverse series, which cannot be fairly appreciated by a study 

 of the few survivors. Nor does the palceontological evidence bear out 

 the separateness of Teleosteans and Ganoids. 



Gi-inther distinguishes the sub -class Teleostei from the sub -class 

 Paloeichthyes, including under the latter the Chondropterygii (Elasmo- 

 branchs and Holocephali) and the Ganoidei (along with which Dipnoi 

 are ranked). As two other sub-classes of Fishes, he recognises the 

 Cyclostomata and the Leptocardii (Aniphioxus). 



Beard proposes the following classification of Ichthyopsida, insisting 

 especially on the separateness of Dipnoi from Ganoids, and on their 

 nearness to Amphibians : — 



riNIarsipobranchii (Cyclostomata). 

 Ganodichthyidae. \ Ganoidei. 

 ( Teleostei. 



Selachodichthyidje.-! t,^ ^'' "',,, ■, fDipnoi. 



\PneumichthyKte.|^_^pj^;^^;^^ 



