of the Fishery Board for Scotland. 



123 



first and the last meet but do not overlap ; they each overlap the range of 

 variation of this character in minutus. In the distance of the opercular 

 cleft from the anterior end of the body we obtain the same average in 

 each species, and in respect to the hind edge of the operculum, while 

 the averages differ to the extent of 2 per cent, between minutus and 

 esmarkii, each of these differs from luscus by 1 per cent. only. 



The position of the pectoral fin is practically the same in all three 

 specie's in respect to the distance of the base of the first fin-ray irom the 

 anterior end of the fish. The distance of the anus from the snout is a 

 diagnostic difference between luscus and minutus. In the average, the 

 position is at 26 per cent, in the former and at 32 at the latter ; the 

 ranges of variation do not overlap. In esmarkii the anus is on the 

 the whole slightly farther back than in minutus, with, of course, a corres- 

 pondingly greater divergence from luscus. Between esmarkii and 

 minutus the ranges of variation overlap. 



In the position of the first dorsal fin, there is very close agreement, and 

 overlapping. 



In the second dorsal fin all three overlap, both in respect to the point 

 at which the fin begins, and also in the position of the end of the fin. 

 Luscus and minutus have a longer fin-base than esmarkii. 



In respect to the beginning of the third dorsal fin, they are all equal, 

 but as luscus has a shorter fin-base than the two others — the fin ends in it 

 a little farther anteriorly than in the other two. 



The first anal fin commences close behind the anus ; it ends first in 

 esmarkii, and then a little distance farther posteriorly in minutus and 

 luscus. 



In the matter of the second anal all three species agree, both in its 

 commencement and its end. 



The caudal peduncle is on the average smaller in luscus than in 

 esmarkii and minutus, but the ranges of variation overlap. 



The bend in the lateral line rises farther back in luscus than in the 

 other two. It is usually just behind the middle of the length of the 

 body ; in no case in luscus did it commence on the anterior half of the 

 body ; in minutus and esmarkii it did in some cases begin just on the 

 anterior side of the middle of the body. The lateral line rises more 

 rapidly in luscus than in minutus and esmarkii. 



The general relation between the three forms in respect to the different 

 characters selected has been briefly discussed, but these relationships 

 expressed in this form are of themselves of no value from the point of 

 view of specific description. These characters may and do indicate 

 where specific characters may be found. For a specific description it is 

 necessary that the selected characters be tested on one fish. - A specific 

 character which infers comparison with a fish of another species is of 

 only secondary value. Each character must be expressed in terms of the 

 individual fish. The size of the eye, for example, may be of specific 

 value when it is stated in terms of the length of the snout, or of any 

 other part of the fish, while it is of no value when compared to the size 

 of the eye in another species. 



I The position of the anus is a very good guide in diagnosing certain 

 species, aud it is important in the present case. The form in which 

 it is represented in the Tables, as being situated at a certain per- 

 centage of the length of the fish from the tip of the jaws, is not a useful 

 one for a specific description. It should be expressed in a relationship 

 that is more readily measured, and for this the relation between the posi- 

 tion of the anus and the situation of the first dorsal fin. Now, an 

 examination of the measurements of the distance of the two points shows 



