AGONUS DECAGONUS. 
207 
ous canals, which are furnished with small, raised, 
tubular openings, on the forehead between the supra- 
orbital spines and on the occiput between the occipital 
spines, respectively. The ventral tins, which in their 
structure — with only two soft rays and with the spi- 
nous ray hidden in the connexion between it and the 
outer soft ray — remind us of certain species among the 
Cotti, also give us a sexual distinction, as Lutken was 
the first to point out, which likewise calls to mind the 
Cotti. In the males the outer soft ray is considerably 
elongated, measuring somewhat more than \\ % of the 
length of the body or about half the distance from the 
insertion of these tins to the beginning of the anal tin; 
while in the females the length of the ventral fins is 
much less, being only slightly more than, or equal to, 
the longitudinal diameter of the eye. 
Agonus decagonus attains a length of at least 21 
cm. It is an arctic form, first discovered in Green- 
land, and subsequently found by 0. Torell in Beru 
Fjord (Iceland) and by the Finnish explorers Nylander 
and Gadd in Varanger Fjord (Norwegian Finmark). It 
was found by the Norwegian Arctic Expedition of ’76 — 
78 at a considerable depth (between 123 and 260 
fathoms) and in very cold water ( + 34' 7 Fahr. to + 30‘2 
Fahr.), on clayey and stony bottoms, in the Arctic 
Ocean round Bear Island and Spitzbergen. The Swedish 
Expedition of 1868 found young specimens, 21 mm. in 
length (in all probability not more than a month old), 
near the surface, where the water Avas 3 or 4 fathoms 
deep, in Liebde Bay, Spitzbergen, on the 29th of 
August. One of these specimens is here figured. 
In this species, as in the following one, the colour- 
ing is distributed according to the typical arrangement 
in Coitus. It is yelloAvish gray, Avith dark transverse 
Fig. 60. Young specimen of Agonus decagonus , Liebde Bay (Spitz- 
bergen), taken at the surface, 29th Aug., 1868. Malmseen and Smitt. 
bands, the situation of Avhich is more minutely shoAvn 
in the figure (p. 205). 
Instead of giving a more detailed description Ave 
may refer to the following table, Avhich gives the most 
important relations of form in the two specimens of 
the Royal Museum from Greenland, side by side with 
which we have set the corresponding measurements in 
three specimens of the following species. We may here 
trace the tendency of the changes of growth and the 
consequent relative position of the tAvo species, as Avell 
as the respects in Avhich constant specific characters 
appear, to judge by the materials at our disposal. 
a 9 
onus cataphractus 
Agonus decagonus 
from Greenland. 
from 
from 
from 
Bohusliin. 
Hammerfest. 
Bohusliin. 
Length, of the body expressed in millimetres 
76 
162 
93 
121 
178 
,, „ head in % of the length of the body 
21.3 
21.3 
21.5 
21.5 
20.8 
Longitudinal diameter of the eye „ „ „ „ „ „ „ „ 
5.5 
5.5 
4.8 
4.3 
3.9 
Distance between the first dorsal fin and the tip of the snout „ „ „ „ „ „ ,, „ 
28.3 
29.6 
32.2 
33.9 
33.2 
Distance between the insertion of the ventral fins and the beginning of the anal fin „ „ „ „ „ „ „ „ 
19.5 
22.4 
23.9 
25.o 
25.5 
Least depth of the tail „ „ „ „ „ „ „ „ 
2.i 
2.o 
3.i 
3.3 
2.8 
Breadth of the body across the base of the pectoral fins „ „ „ „ „ „ ,, „ 
12.5 
14.2 
17.1 
19.9 
20.3 
Depth ,, „ ,, at the beginning of the first dorsal fin ,, „ „ „ ,, ,, 
10.5 
12.7 
12.7 
13.7 
13.7 
Least depth of the tail in % of the length of the head 
9.9 
9.3 
14.5 
15.4 
13.5 
„ ., ,, ,, ,, ,, ,, longitudinal diameter of the eye 
38.i 
35.5 
64.4 
76.9 
71.4 
„ „ „ „ „ „ „ „ „ least breadth of the interorbital space. 
12.i 
40. o 
58.o 
66.7 
53.7 
„ „ „ „ „ „ ,, „ „ length of the lower jaw 
23.5 
20. o 
48.3 
40. o 
35.7 
„ „ ,, ,, „ ,, distance between the first dorsal fin and the tip of the snout 
7.4 
6.7 
9.7 
9.7 
8.5 
„ „ „ „ „ „ „ „ „ height of the first dorsal fin 
— 
26.7 
32.2 
38.4 
„ ,, „ „ „ „ „ „ „ „ „ „ second „ „ 
— 
18.8 
35.3 
. 
34.5 
,, ,, ,, ,, „ ,, ,, ,, length of the base of the anal fin 
18.2 
22.8 
27.3 
30. o 
23.5 
Distance between the insertion of the ventral fins and the beginning of the anal lin in % of the distance be- 
tween the anal fin and the (ip of the snout 
47.1 
49.6 
53.i 
54.1 
55.5 
Breadth of the body across the base of the pectoral fins in % of the length of the head 
59.2 
66.7 
78.5 
92.3 
97.3 
Length of the ventral fins in % of the length of the pectoral fins 
45.i 
51.5 
55.o 
68.2 
62.i 
„ ,, „ „ ,, ,, „ „ „ distance between the insertion of the ventral fins and the beginning of 
the anal fin — 
40 5 
49 8 
54 5 
49 5 
45 o 
Length of the head in % of the distance between the first dorsal fin and the tip of the snout . 
75.3 
71.9 
66.7 
63.4 
62.7 
