-ON THE SPECIFIC CHARACTERS OF THE HADDOCK 

 (GADUS JEGLEFINUS, LINK), WHITING (GAD US 

 ME RL ANGUS, LINN); GADUS POUT AS SOU KISSO ; 

 GADUS ARGENTEUS, GUICHENOT ; GADUS SAID A, 

 LEPECHIN; GADUS OGAC, RICHARDSON; GADUS 

 NAVAGA, KOLREUTER; with a Key to the Species of 

 Gadus 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 of the Leng 



Fish, . . . . . . 



Tables showing the numbers of Vertebras, Fin-rays, and Pyloric 



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, 



fch 



of the 

 Caeca in 



PAGE. 



97 

 97 

 98 

 99 



160 



105 



111 

 120 

 123 

 123 

 124 

 125 

 130 

 13) 

 132 



INTRODUCTION. 



This paper continues the research on the classification of the Gadicla?. 

 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. J oh. 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. Breitfuss, St. Petersburg, for a specimen of G. saida. 

 Dr. Hector Jungersen, Copenhagen, also kindly favoured me witii th* 

 loan of G. ogac and G. navaga. 



TJie Fishes Examined. 



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

 obtained were as follows : — 



