88 
MR. F. DAY ON THE LOC1I-LEVEN TROUT. 
Leven trout, but in a double row in burn-trout of the same size, we 
have first to consider whether the facts as stated are correct. All 
trout and salmon (not charr) when young, irrespective of the teeth 
on the head of the vomer, have a double row along its body ; but 
these in all are dependent on age or rapidity of growth, and fall 
out, commencing behind and extending forwards. In salmon and 
sea-trout, which are forms that grow most rapidly, these teeth are 
shed the earliest, while the Loeh-Leven trout, which is likewise a 
rapid grower, loses them rather sooner than the burn or loch 
form; hence to say that in the mature examples they are invariably 
in a single row is erroneous. At the same time it is not here 
advanced that rapidity of growth is the sole cause of this, for 
the deciduousuess of the teeth appears to be owing to the absorp- 
tion or narrowing of the tooth-bearing ridge on the vomer, in 
consequence of which the teeth, originally placed in pairs, become 
ultimately ranged in a single row and finally fall out. 
The condition of the vomerine dental system in specimens of 
Loeh-Leven trout may be thus recorded : — (1) $ 20 inches 
long, 2 teeth exist on the hind edge of the head of the vomer, 
and 3 along the front half of its body, the first two of which 
are almost opposite one another. (2) S 9 inches long, 2 
teeth at hind edge of vomer, 2 at the front end of the shaft, 
and 7 in an irregular zigzag line, almost in one continuous row, 
while their points turn alternately to the right and left. (3) § 
109 inches long, 2 at hind edge of head of bone, 2 in a line 
at the commencement of the body, and 8 as in the last but more 
distinctly in pairs. (4) $ 13’5 inches long, 2 at hind edge of 
head of vomer, then 4 in a single row, next a pair turning one to 
each side, and lastly 4 more single ones. (5) <5 14 inches long, 
2 teeth at hind edge of head of vomer, 9 in a single row along 
the body of that bone ; of these the two central ones form a pair. 
(6) $ 19'2 inches long, 4 teeth at hind edge of body of the 
vomer, 12 along the body, among which are three pairs. (7) $ 
23 inches long, 3 at hind edge of head of vomer, 8 along its body 
in a single row, some turning one way and some another. 
The foregoing seven specimens show that it is by no means an 
invariable rule that all the teeth along the body of the vomer are 
in a single row. 
Having examined a considerable number of burn or loch trout 
in Sutherlandshire, I found that the maxillae were not stronger 
thau in the Lochlevens, while a specimen * taken at random 
* Exhibited when the paper was read. 
