190 Transactions, — Zoology. 



six years these fish have now been in our harbour, have seen or heard of 

 the young fry being in these streams, but we liave not. Such a thing as a 

 sea-trout spawning in salt water is unknown, and it will be very surprising 

 if our S. trutta are found so to do. There is thus a mystery as to the habits 

 and movements of our S. trutta, sufficient almost to throw doubt on their 

 identity. Still we are in this position — we have a trout got only in the salt 

 water, specifically differing from the common trout of our streams, and 

 agreeing in its distinguishing marks with 8. trutta. It is caught in the salt 

 water varying in weight from 1 lb. to 18 lbs,, and is often found in spawn- 

 ing condition in the beginning of our summer. Hitherto no well verified 

 example has been taken in any of our streams. Much remains, therefore, 

 to be discovered of the habits in our waters of this fish, which I do not 

 doubt, after the examinations I have made, is the real Salmo trutta. 



The sea-trout of Otago were brought from Tasmania as ova by Mr. 

 Clifford, 137 young fish being turned into Shag river in 1871, at which 

 time also I understand a few more were put into the Water of Leith, at 

 Duncan's mill. 



Distinguishing Marks. 



These marks, I will endeavour, in closing this paper, to summarize 

 briefly ; and in doing so I may say that I give them partly from my own 

 observations, and partly as I find them given by the best authorities. They 

 refer only to adult fish. 



Of the S. quinnat and S. paucidens, I cannot venture to lay down from 

 my own experience rules for their identification from other salmon of the 

 same genus, the Oncoryyichus, as my knowledge of these fish is as yet very 

 limited. It would require years of residence and study in California or 

 Columbia to acquire such knowledge correctly, and as yet I have not been 

 able to find any author who gives a full and accurate description of these 

 fish. At the same time there is no difficulty in recognizing the difference 

 between these and the Salmo salar. They belong to a different genus, the 

 Oncorynchtis, where the anal rays exceed 14, while in the 8. salar these are 

 always less, being rarely more than 10.* 



But of the 8. salar I may say that it may be most readily distinguished 

 from the other species {8. trutta and 8. fario) of the genus 8almo, by its 

 strong and uniform coating of burnished silvery scales, 12 in transverse 

 row fi'om adipose to lateral line ; its fine sharp and clean-cut head ; its 

 arched back and deep belly, its taper and cylindrical shape towards the tail, 

 its large square tail, sometimes emarginate ; by the fewness, anda'-shape of its 



* Mr. Lord describes the margin of the operculum as having spinous projections which 

 give it a serrated form. 



