34 David Starr Jordan 



the different species. From this table it was made evident 

 that in that group of flounders,* which includes the halibut 

 and its relatives, the arctic genera t have from 49 to 50 verte- 

 brae. The northern general have from 43 to 45, the members 

 of a large semi-tropical genus § of wide range have 35 to 41, 

 while the tropical forms || have from 35 to 37. 



In the group of turbots T[ and whiffs none of the species 

 really belong to the northern fauna, and the range in numbers 

 is from 35 to 43. The highest number, 43,** is found in a 

 deep water species, and the next, 41 and 40, tt i'l species 

 which extend their range well toward the north. 



Among the plaices, which are all %% northern, the numbers 

 range from 35 to 65, the higher numbers, 52, 58, 65, being 

 found in species §§ which inhabit considerable depths in the 

 arctic seas The lowest numbers {||| (35) belong to shore 

 species which range well to the south. 



Concerning this matter, Jordan and Goss remark : 



It has already been noticed by Dr. Giinther and others that in certain 

 groups of fishes northern representatives have the number of their ver- 

 tebra increased. In no group is this more striking than in the 

 flounders. 



Gill, 1889. — In a review m[ of the paper above mentioned, 

 Dr. Gill considers in detail the condition of our knowledge of 

 this subject, quoting from the various papers mentioned above 

 and claiming very properly that the first statement of this 

 generalization belonged to himself rather than to Dr. Giinther. 



Dr. Gill further adds : 



The case of the sebastines became still more striking when Messrs. 

 Jordan and Gilbert discovered that the number of vertebrae in the 

 species of Sebastichthys and Sebastodes, genera intermediate between 

 the northern Sebastes and the tropical and subtropical representatives of 

 the family of ScorpcznidcE , was also intermediate. 



* Hippoglossintz. f Hippoglossus and Atheresthes. 



XHippoglossoides, Lyopsetla, a.nA Eopsetta. 'iParalichthys. 



II Xystreurys, Ancylopsetta, etc. \ Psettinos. 



** Monolene sessilicauda. \-\ Lepidorhonibus -vhijf-jagonis and 



Citharichthys sordidus. 



X\ Pleuronedince. H Glyptocephalus and Dficrostoinus. 



WW Platichthys stellatus, Hypsopsetta guttulata. 



\\ Proceedings of the U. S. National Museum, 1S88, p. 604. 



