of the Fishery Board for Scotland.. 



335 



IX. — THE CLASSIFICATION OF THE FLAT-FISHES (Heteroso- 

 mata). By H. M. Kyle, M.A., B.Sc, Science Scholar, St. Andrews. 

 (Plates XL, XIL). 



CONTENTS. 



Introduction ....... 



Description of Characters ..... 



Characters of most importance for classification 

 Classification ....... 



Geographical Distribution ..... 



INTRODUCTION. 



The present work was begun during the winter of 1898-99 at St. 

 Andrews, was continued as time and opportunity permitted at Heligo- 

 land, later at the British Museum of Natural History, and at the 

 Zoological Station at Naples. The opportunities thus afforded for the 

 examination of material — both fresh and in spirit — were exceptional, 

 and a much larger number of specimens and of species have passed 

 through my hands than I had at first thought of or hoped for. I have 

 to thank Prof. Mcintosh, F.R.S., of St. Andrews, and Prof. Heincke 

 and Dr. Ehrenbaum of Heligoland, for the use of the Marine Labora- 

 tories at St. Andrews and Heligoland ; Mr. Boulenger, F.R.S., especially 

 for the kindness, encouragement, and aid I received whilst working at 

 the British Museum of Natural History ; also the British Association 

 for the Advancement of Science, through the secretary, Prof. Howes, 

 F.R.S., for the honour of occupying their Table at the Naples Marine 

 Station ; and the stall of the latter for much kindness and courtesy. 



The species which have been examined include the majority of the 

 European forms, representatives of the chief genera of the American 

 flat-fishes, and of those of the Indian, China, and Australasian seas. 

 In spite of the large number of species which has been examined, the 

 number unexamined is very much larger, so that the present classifica- 

 tion does not profess to be complete, but merely offers a certain outline 

 into which the various groups fit, and displays in a manner easily 

 grasped the gaps in our present knowledge of these forms. The origina 

 aim was to trace out the natural affinities of the various sub families 

 and the changes in their characters with geographical distribution, by 

 the study of their internal structure as well as of their external 

 characteristics. The results that have come to the surface, and perhaps 

 one might say the " cream " of the work which has been done, are here 

 gathered together into the present paper, and it is hoped — if the oppor- 

 tunity is given — to enter more in detail into the anatomy and develop- 

 ment of the flat-fishes, and thence be able to eliminate the shortcomings 

 of the present work, and give fuller descriptions of the specific and 

 generic differences within the Ilekrosomata. 



External Characters, 



The great majority of the external characters — scales, coloration, fin- 

 rays — are only of specific importance in the Heterosomata. These are 

 characters which vary greatly and give rise to great difficulties even in 



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