504 Transactions.— Miscellaneous. 
they are found by me 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 versà. ` 
The eye in females is relatively nearer to the snout than in males. 
The teeth of the vomer have been regarded by Dr. Günther and others 
as a good character to fix the S. fario species as distinct from the S. trutta 
species. That is, while the vomerine teeth in the latter are deciduous, those 
of S. fario are described by Dr. Günther 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, pl. 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 eurves. "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 
