of the Fishery Board for Scotland. 121 
vreater accuracy to be obtained on the whole by making the measure- 
ments on such a board as described in the 18th Report, than by merely 
stepping off the distances on the fish with a pair of dividers. If the fish 
are in good condition, in both methods greater accuracy will be obtain- 
able than in specially soft specimens. 
The measurements were made in centimetres. 
The Measurements Represented as Percentages of one Common 
Standard.—All the body dimensions were converted into percentages of 
one standard, viz., the length of the fish. 
THe LenerH or tHE Fis is the distance from the anterior tip 
(premaxilla or mandible, as the case may be) to the end of the middle 
rays of the tail fin. 
The fishes of each species have been arranged in centimetre groups. 
The average of the percentages of the length of the fish which each body 
dimension was found to represent was calculated for the fishes of each 
size. They have been arranged in Tables VII, VIII, IX, X, XI, XII. 
Alongside each average is added in brackets the number of fishes on 
which the average is based. 
The average percentage for each character has then been calculated in 
ali the fishes of each species in which the character was noted. The 
number of characters examined in each specimen varied very much; 
while in some all the characters were noted, in others one or two 
characters were measured. 
Enumeration- Characters. 
THe Number or Rays iy THE Unpatrgp Frns.—The enumeration 
of the fin-rays is rendered difficult from the fact that we are dealing with 
small fishes. he last rays in the fins with the exception of the first 
dorsal are minute. The first rays of the first anal fin are sometimes 
liable to be missed on account of their very small size. 
In a few cases the number of rays in the paired fins and the caudal fin 
was counted. 
Tue Number or VerTEBR#.—The number of vertebree was counted 
after the fish had been boiled. The posterior vertebre are very small ; 
the backbone tapers down to a fine extremity. The vertebre are not so 
easily counted in preserved fishes as in fresh specimens, A fish that has 
been preserved in formaline solution, when boiled, usually becomes 
distorted. This is due to unequal shrinkage : the skin i is much affected 
in this respect, becoming very tough. The vertebra bearing the ural 
elements is counted as the last vertebra. 
THE Number oF THE VERTEBRA BEARING THE First H#MAL 
ArcH.—This character was noted in a number of instances. 
DiscussioN OF THE Bopy DIMENSIONS. 
The averages taken along with the range of variation of the character 
gives a more or less partial view of the species, By a comparison 
between the species we shall be able to see in how far any of these 
dimensions is of specific value. If we find that the ranges of variation 
in two species overlap for any one character, that character cannot be 
regarded as of primary rank in a specific description. In a dimension of 
which the ranges of variation do not overlap in two species we have a 
character of primary rank. The characters as set out in Table XIII. will 
now be examined in detail. 
