504 Transactions. — Miscellaneous. 



they are found by nie to become angular in the subopercle, and sinuous 

 in the operculum and preoperculum. A careful comparison of trout heads 

 preserved by me, shows that sex has no influence on the form of the sub- 

 opercle ; or that the particular form does not indicate the sex. Neither 

 does residence in brackish or salt water appear to affect the shape of that 

 bone ; but I have not as yet had more than a few specimens to examine, 

 taken in salt water. 



The branchiostegal rays which I have carefully counted in many of our 

 trout are pretty constant at 10 in number. They vary, however, sometimes 

 from 9 to 11, and it is a common occurrence to find one more on the left 

 side than the right or vice versa. 



The eye in females is relatively nearer to the snout than in males. 



The teeth of the vomer have been regarded by Dr. Gunther and others 

 as a good character to fix the S. fario species as distinct from the 8. trutta 

 species. That is, while the vomerine teeth in the latter are deciduous, those 

 of 8. fario are described by Dr. Gunther as " persistent through life." 

 Now, whatever the case may be in the trout of Home rivers, I have abun- 

 dant proof in my notes, made when examining the teeth of Otago trout, 

 that they are very far from being persistent on the vomer. On the head of 

 the vomer (excepting in the case of a trout from the Wakatipu, got in 

 January, 1880) I have always found the teeth present. But, on the shaft 

 of that bone, the gradual disappearance, year after year, of the teeth, is from 

 behind forwards, and appears to be mainly a consequence of the increased 

 age of the individual trout. 



The body of the trout in outline is much more varied than one would 

 suppose, and this is, I venture to think, the explanation of the difficulty 

 anglers find in guessing correctly the weight. Thus, taking the case only 

 of trout when in good or fair condition, the back is sometimes so slightly 

 arched as to be nearly straight, the belly in such a case being very deep and 

 full (see fig. 2, pi. xliii.) ; so much so, indeed, as (with exceedingly fat 

 fish) to distort the mouth, and throw the ventrals nearer the tail. Then 

 our best-shaped trout are hog-backed from the head to the dorsal fin — both 

 back and belly being properly balanced in their curves. There are also two 

 distinct forms when viewing trout transversely : the one is narrow and deep 

 in section, the other broad across the back, and not at all deep in section. As 

 already mentioned, I find in good fat fish the minimum ratio of depth to 

 girth should be as 1-2^. I have not much to say about the form of the 

 fins, excepting that as regards the tail, or, as I should perhaps name it, the 

 caudal fin, I find it forked in our young trout ; in mature fish of 2 lbs. it 

 often is forked also ; but, in heavier and presumably older fish, it varies 

 from slightly emarginate to straight* and sometimes even truncate. I have 



