Mr. J. Blackwall on the Salmon and Bull-trout. 243 
salmon and actually curved outwards in the bull-trout, thus 
supplying the means of forming a comparative estimate of the 
ages of both species. 
In accordance with what is here stated, I find that specimens 
weighing from half a pound to a pound and a half have the 
caudal fin more or less forked, and the vomer well supplied with 
teeth except at its posterior part, from which some are lost in- 
variably. Specimens weighing from two to five pounds have 
the posterior margin of the caudal fin either moderately forked, 
nearly straight, or curved outwards, according to their size and 
species, and usually have from three to seven or eight teeth on 
the anterior part of the vomer, the number, after making a suitable 
allowance for differences in condition, being almost always in- 
versely as the weight; and individuals of large dimensions con- 
stantly have the posterior margin of the caudal fin straight or 
conspicuously curved outwards, and retai one or two teeth 
only at the anterior extremity of the vomer, or are even without 
any. 
eae salmon and bull-trout weighing from about half a 
pound to a pound ascend the river Conway during the month of 
August in much greater numbers than at any other period of the 
year, and as many of them are infested with that marine parasite 
the Caligus curtus of Miiller in various stages of growth, there 
can be no doubt that they have very recently quitted the salt 
water. These fish, which from oft-repeated examinations of 
numerous individuals are found to have the tail forked in a 
greater or less degree, and uniformly to have lost some teeth 
from the posterior part of the vomer, though its anterior part is 
still amply provided with them, I feel thoroughly convinced are 
identical with smolts of both species which descended the same 
river in the preceding spring, having then the full complement 
of teeth on the vomer; for salmon and bull-trout of smaller 
dimensions do not at any time come up the Conway from the 
sea, as may be ascertained by actual inspection in calm bright 
weather, when the water is low and clear and the shoals of fish 
can be distinctly seen; and if further proof be required, it is 
abundantly supplied by the conclusive evidence obtained from 
the large number of specimens taken annually. It is true that 
I have occasionally procured salmon and bull-trout in the months 
of March and April which have weighed six ounces only, but 
they have always been males which had milted or females which 
had deposited their ova and were out of condition, or what in 
Scotland are denominated kelts. 
I shall here introduce to notice a few examples illustrative of 
the loss in weight which salmon and bull-trout undergo by the 
act of spawning. 
16% 
