4 FLATFISHES (HETEROSOMATA1 



of tlic " Solos " (Solcidac and Cynoglossid.'c) may possibly provide evidence of ttieir 

 origin from a stock of I'ercoids different to that which gave rise to the " Flounders ".' 

 Genera intermediate between Pscttodes and the more specialised Flatfishes do not 

 exist to-day. but it is not difficult to see how such a form as Payalichthys or Athcresthes 

 might have been derived from this primitive genus. In considering the origin of the 



—Eptnephdus Uaiar 

 J.) c, Tectoral arc 

 5 (,- J). I.etlering; 



Heterosomata as a whole, therefore, instead of comparing the highly specialised 

 Turbot with the John Dory, or the Halibut with the Cod, it is clearly of greater 

 importance to compare Pseltodes itself with representatives of the groups of fishes 

 from which the Flatfishes are believed to have been derived. Leaving out of 

 consideration the aberrant Allotriognathi, it will be convenient to consider in turn the 

 evidence both for and against a Gadoid. Zeoid and Percoid ancestry respectively. 



' Si'e p. .17- 



