of the Fishery Board for Scotland. 



97 



V.— ON THE SPECIFIC CHARACTERS OF THE HADDOCK 

 (GADUS jEGLEFINUS, LINK), WHITING (GADUS 

 MERLANGUS, LINN.); GADUS POUTASSOU, RISSO ; 

 GADUS ARGENTEUS, GUICHENOT ; GADUS SAIDA, 

 LEPECHIN; GADUS OGAC, RICHARDSON; GADUS 

 NAVAGA, KOLREUTER ; with a Key to the Species of 

 Gad us found in Northern Waters. By H. Chas. 

 Williamson, M.A., D.Sc, F.R.S.E., Marine Laboratory, 

 Aberdeen. (Plates VIII.-XIII.) 



CONTENTS. 



Introduction, .... 

 The Fishes Examined, 

 External Characters — Body -Dimensions, . 

 Enumeration Characters, 



Table showing the Measurements as Percentages 

 Fish, ..... 



Tables showing the numbers of Vertebrae, Fin-ray 

 the different species, . 



Key, ...... 



The Skulls, etc., .... 



Diagnostic Value of certain Bones, 



The Diagnosis of Isolated Bones, . 



The Rib (Pleurapophysis), . 



Notes on the Species, 



Literature, ..... 

 Letters used in the Plates, . 

 Explanation of the Plates, . 



of the 

 s, and 



Lengtl 

 Pyloric 



of the 



Cseca in 



PAGE. 



97 

 97 

 98 

 99 



100 



105 

 111 

 120 

 123 

 123 

 124 

 125 

 130 

 131 

 132 



INTRODUCTION. 



This paper continues the research on the classification of the Gadidse. 

 The two preceding parts were published in the Twentieth and Twenty- 

 fourth Annual Reports of the Fishery Board for Scotland, Part III., in 

 1902 and 1906. They dealt with six species, and in the present con- 

 tribution the remaining seven species are discussed. 



I have been indebted to several zoologists for the courteous supply of 

 specimens of the rarer species, and my thanks are specially due to 

 Mr. E. W. L. Holt, Dublin, Drs. Job. Schmidt and A. C. Johansen, 

 Copenhagen, for examples of G. poutassou and argenteus ; to Professor 

 Brandt, Kiel, Dr. Pappenheim, Berlin, and Professor Vanhbffen, 

 Charlottenburg, for specimens of G. saida and the loan of examples of 

 G. ogac ; and to Dr. Breitf uss, St. Petersburg, for a specimen of G. saida. 

 Dr. Hector Jungersen, Copenhagen, also kindly favoured me with the 

 loan of G. ogac and G. navaga. 



The Fishes Examined. 



The sizes of the fishes (in cm.) and the localities from which they were 

 obtained were as follows : — 



