Temperature and Vertebrce 



25 



In the family of flounders or Pleiironectidcs , a group of 

 wide distribution and in which the individual vertebrae are 

 numerous and little specialized the results are especially strik- 

 ing. 



In each of the four principal groups, the numbers agree 

 closely with the geographical distribution of the different 

 genera. Thus in the comparatively primitive subfamily of 

 Hippoglossince, the halibut group, the division nearest the 

 cod-like stock from which the flounders are probably de- 

 scended, the numbers range from 35 to 50. In the turbot 

 %ro\\^ (^Psettinire) from 31 to 43. In the plaice group, {Plett- 

 ronedincB) 35 to 65. In the sole group, {Solemcs) 28 to 49. 

 The tongue-fishes i^Cyyioglossincs) are elongate like the eels, 

 and specialized in analogous ways. Although all tropical, 

 the numbers counted range from 47 to 52.* 



Fresh Water Fishes. — Of the families confined strictly to the 

 fresh waters the great majority are among the soft-rayed or 

 *These facts may be shown in tabular form as follows : 

 HlPPOGIvOSSIN^. 



Hippoglossus, 50, Arctic. 

 Atheresthes, 49, Arctic. 

 Hippoglossoides, 45, Subarctic. 

 Lyopseita, 45, Subarctic. 

 Eopsetta, 43, Subarctic. 



PSETTIN^. 



Motioleite, 43, Deep Sea. 

 Lepidorhoinbus, 41, Arctic. 

 Orchopsetia, 40, Subarctic. 

 Platophrys, 37 to 39, Tropical. 

 Arnoglossus, 38, Semitropical. 

 Zett^opterus, 37, Temperate. 

 Bothiis, 36 Temperate. 

 Syacimn, 35 to 36, Tropical. 

 Citharichthys, 34 to 36, Tropical. 

 Phrynorhombus, 35, Semitropical. 

 Etropus, 34, Tropical. 

 Azevia, 33, Tropical. 

 Psetta, 31, Tropical. 



Psettichthys, 40, Subarctic. 

 Paralichthys, 35 to 41, Temperate 



and Semitropical. 

 Xystreurys, 37, Semitropical. 

 Ancylopsetta, 35, Semitropical. 

 PlvEURONECTIN^. 



Glyptocephalus, 58 to 65, 



Arctic and deep sea. 

 Microstomus, 48 to 52, 



Arctic and deep sea. 

 Parophrys, 44, Subarctic. 

 Pleuronectes, 43, Subartctic. 

 Isopsetta, 42, Subarctic. 

 Lepidopsetta, 40, Subarctic. 

 Lhnanda, 40, Subarctic. 

 Liopsetta, 40 Subarctic. 

 Pleuronichthys, 38 to 40, 



Temperate. 

 Flesus, 36, Temperate. 

 Pseudopleuronectes, 36, 



Temperare. 

 Hypsopsetta, 35, Semitropical. 

 Platichthys, 35, Subarctic. 



