REPORT OF COMMISSIONERS OF INLAND FISHERIES. 59 



j HIPPOGLOSSIN.E. 



[(Halibut, Summer Flounder, 

 Four-spotted Flounder, 

 Rusty Dab.) 



\ 

 I 



( PLEURONECTIN.E. 



HETEROSOMATA. ' PLEURONECTiD.E. j (Winter Flounder, Rusty 



(The Fiat-Fishes.) \ (-The Flounders.) j Fiat-Fish.) 



PSETTIN.E. 



(Window-Pane.) 



SOLEID.E. ( ACHIRIN.E. 



(The Soles.) ( (American Sole). 



The ancestry and kinship of the flat-fishes are wholly uncertain. 

 They have usually been placed with the cod-fishes, and it has been 

 assumed that both these groups have descended from some common 

 or nearly related form; it is, however, with much reason that Dr. 

 Boulenger has recently called attention to the close relationship of 

 the flat-fishes to the Zeoidea (the John Dories, or Zeus-like fishes), 

 and he suggested that both these types may have descended from a 

 common stock. 



There are some interesting facts regarding the geographical dis- 

 tribution of the various species of the flat-fishes. The fishes of the 

 Flounder tribe (Plewonectince) and almost all of the Halibut tribe 

 (Hippoglossince) are arctic and antarctic in their distribution; the 

 species belonging to the Turbot tribe (Psettince) are nearly all con- 

 fined to warm water. Since all the fishes of the Turbot tribe, and 

 those of the Halibut tribe which are found in warm water are left- 

 sided species, while the cold-water halibuts and all of the Flounder 

 tribe are right-sided species, it follows that nearly all the warm- 

 water flounders are left-sided species and the cold-water flounders 

 are right-sided. This peculiar relation may be a coincidence merely, 

 but it is certainly veiy remarkable that we should find the 

 Summer Flounder and the Four-Spotted Flounder and a few other 

 species of that group to be left-sided and in warm water, while the 

 majority of the fishes of that tribe are right-sided and inhabit cold 



