110 TEMPERATURE AND FISH VERTEBRiE JORDAN. 



ber of vertebrip, of Sebastes, a geuus peculiar to tbe northern seas, 

 aflbrds an excellent example of the truth of the generalization claiming 

 an increased number of vertebrai for the cold-water representatives of 

 Acauthopterygians. 



Jordan, 1886. — In 1886, in a paper before the Indiana Academy of 

 Sciences,"* the present writer showed that in very many families the 

 number of vertebr.e decreases as we approach the tropics. So constant 

 is this relation that it was thought that it might almost be termed a 

 law. The writer could however suggest no adequate cause by the oper- 

 ation of which such changes are brought about. 



Jordan and Goss, 1889. — In a study of the flounders, in 1889,t a table 

 was given showing the numbers of vertebne in 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 § have 

 from 49 to 50 vertebrae The northern geuer<i|j have from 43 to 45, the 

 members of a large semitropical geuus^ of wide range have 35 to 41, 

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



In the group of turbotstt and wliiffs none of the species really belong 

 to tiie northern fauna, and the range in numbers is from 35 to 43. Tlie 

 highest number, 43,|J is found in a deep water species, and the next, 41 

 and 40,§§ in species which extend their range well toward the north. 



Among the plaices, which are all |||| northern, the numbers range from 

 35 to 05, the higher numbers, 52, 58, 65, being found in species ^1^] 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 north(3rn representatives ]iave the nnmber of their vertebra? increased. In no 

 group is this more striking than in the dounders. 



Gill, 1889. — In a review ttt of the paper above mentioned. Dr. Gill con- 

 siders in detail the condition of our knowledge of this subject, (pioting 

 from the various papers mentioned above, and claiming very pro[)erly 



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 Gil- 

 bert discovered that the number of vertebra} in the species of Sehastichihys and Sebas- 



* Still unpublished. 



tA Review of the Flounders and Soles (Pleuronectidce) of America and Europe, by 

 David S. Jordan and David K. Goss. 

 t HippodlossuHv. § HlpimrjlossuH and Aiheresthes. 

 II Hippotjlossoides, Lyopselta, and Eopsetta. H Paralichthys. 

 ** Xyfitreitrys, AncylopiscUa, etc. \\ Fsetlinm. 



t\ Monolcne fiesfttlicauda. ^^ LcpidorhnmhuH whiff-jayoitin and CitJiarichthys sordidus. 

 nil rieiironccthin'. 1111 (!hi]>foc(ph<th(s and Microntomufi. 

 *** riaUclithys stellatuH, Hypsopsetta (/nftulata. 

 ttt Proceedings of the U. S, National Museum, 1888, p. G04. 



