BY R. M. JOHNSTON, F.L.S. 43 



uot based upon the casual examinatiou of one or two speci- 

 mens. During the last twelve years I have carefully 

 examined and noted the varying characters (over thii-ty iu 

 each specimen) of hundreds of examples taken in various 

 localities. I have not made final comparison of the relative 

 size of fins and other essential characters of different sized 

 specimens until each absolute measui'ement was reduced to a 

 common equivalent. 



That is, I have been in the habit of regarding the total 

 length of each fish as 1,000, and by computation I have 

 reduced all other parts iu relation thereto. 



In no other way can the observer appreciate with the 

 fullest accuracy the relative agreements and differences of 

 individuals of different sizes and ages. In no other way can 

 the various modifications of locality, age, and variety, be 

 satisfactorily' compared and appreciated. 



That due attention has been paid to the many nice dis- 

 tinctions which characterise the individuality and species of 

 the English and local salmonoids may be admittecl upon 

 reference to the following tabular analyses of the principal 

 typical specimens deposited in the British Museum, for which 

 measurements have been recorded in Dr. Gunther's Catalogue 

 of Fishes, Vol. VI. ; with which typical individuals of the 

 three principal groups of Tasmauian salmonoids are com- 

 pared according to a common standard ; all the measurements 

 have been carefully reduced by me, a work of considerable 

 labour iu itself. 



