124. Part IIL—Twenty-fourth Annual Report 
that among specimens of duscus the anus was situated exactly below the 
beginning of the first dorsal in three cases; in two cases it was in front of 
that point to the extent of 1 per cent. of the length of the fish, and in 
seven cases it was behind the beginning of the first dorsal to the extent 
of 2 per cent. of the fishes’ length. 
In duscus, then, the anus is situated below the beginning of the first 
dorsal fin. 
In minutus the anus occupies a very different position in relation to the 
first dorsal fin. Of 34 examples of minutus, in 31 the anus was below 
the second half of the first dorsal, in one case it was below the middle 
point of the fin, and in two cases it was just in front of the middle point 
to the extent of 1 per cent. of the length of the fish. In mznutus, there- 
fore, the anus is under the second half of the first dorsal fin, z.e., from 
the middle of the fin to the hind limit of its base. The amount by 
which the anus was in front of the middle point of the fin would not 
be noticeable to the eye, and for all practical purposes it would be 
regarded as coinciding with the middle point. 
In esmarkii the anus is below the second half of the first dorsal fin ; 
this was found to be the case in all the fishes in which these characters 
had been recorded—viz., 56 in number. In one of these the anus was 
exactly below the end point of the fin-base. In esmar/ti, then, the anus 
is situated below the second half of the first dorsal fin. 
The comparative depth of the members of the two species, Juscws and 
minutus, has been insisted on in a specific description. It is not, however, 
very easy to reduce this relation to a specific character. In some speci- 
mens it is well marked; but while duscws is always a deep fish, minutus is 
variable in this respect. Sometimes in a collection of mnutus it 1s 
possible to divide them up into two lots differing markedly in the depth 
of body, and in the deeper lot simulating in depth duscus, It is necessary 
to know the range of variation in this character as determined by the 
measurements of various examples. If, therefore, we examine the 
average dorso-ventral height of each species, as set out in Table XIII, we 
find the average height at the anus is, for dwscus, 26 per cent ; for minutus, 
21 per cent.; and for esmarkiz, 18 per cent. of the length of the fish, In 
luscus, however, the depth ranges from 28 per cent. to 22 per cent., while 
in minutus the limits were 24 per cent. and 18 per cent. The relation 
between the two species might be summarised thus :—Where the dorso- 
ventral height reaches one-quarter or more of the length of the fish, we 
have to deal with /Juwsews; where the same character is as small as 
one-fifth or less of the length, the fish is probably minutus or esmarkit; 
but where the relation lies between one-quarter and one-fifth, either of 
the two first species may be represented. It is evident, then, that a 
character such as this is only of small importance for specific diagnosis. 
The Lengths of the Bases of the Unpaired Fine. 
The inter-relations of the sizes of the different fin-bases may be here 
considered. In the following Table the average size of the fin-base, 
expressed as a percentage of the length of the fish, and its range of varia- 
tion is given for each of the three species. 
1D. 2 D. 3D. 
| Species. =e = epee SL ee 
| Max. | Ay. fee | Min. | Max.| Av. Le, Min. | Max.| av.| 47) yin 
| Aa GR i a A aa 
|G. luscus | 13 | ue] 10 | 10 | 27 | 25 | 10 | 24 | is | 127 | 20. | sty 
|G. minutus} 13 | WN?) 34 10 26° | 243) 33 22 LT AS 2 84. 13 
ie esmarkit| 15 12 56 | i) | 25 | 22 | 48 | 20 18 | 165 | 47 12 
