COMMON SEA-SNAIL. 
289 
can scarcely be regarded as a valid one — and ap- 
proaches the fully tadpole-like form of the tail which be- 
longs to the specimens just mentioned, which are far 
from the commonest, even in Spitzbergen. The pecu- 
liarity of the caudal tin, on the other hand, in this 
species is its smaller length, which varies between 11 
and 14 % (occasionally rising, however, to 16'/ 2 %) of 
the length of the body, or between 40 and 65 % of 
that of the head. The adhesive disk formed by the 
ventral tins is also less than in the preceding species, 
its length never rising to 1 j 2 that of the head, and 
sometimes sinking as low as to 36 % thereof. It is some- 
times surrounded even in front by the pectoral fins, a 
dermal flap uniting the latter to each other — this is 
distinctly the case, for example, in a specimen from 
Bravik (a firth of the Baltic Sea), and also in one of 
Lutken’s figures of Cyclogaster Fabricii from Kara Sea 
— but in this species as in the preceding one, there 
is generally an interval between the pectoral fins. The 
position of the vent varies considerably: in a young 
specimen 28 mm. long, from Stor Fjord (Spitzbergen), 
which, however, still retains distinct traces of the larval 
stage, the vent lies close to the beginning of the anal 
fin; in a specimen 53 mm. long, from the same loca- 
lity, the distance between the vent and the anal fin is 
V 3 of that between the latter and the ventral disk; 
and in a specimen 60 mm. long, from the neighbour- 
hood of Visby (Gothland), the former distance is 2 / 3 of 
the latter. In ordinary cases, however, the vent lies 
about half-way between the ventral disk and the anal fin. 
The coloration is essentially the same as in the 
preceding species, and is no less variable. In full-grown 
specimens, however, at least in Sweden, it is usually 
darker, the ground-colour being more distinctly tinged 
with gray; and the brown dots are more often collected 
into transverse bands on the fins and the body. These 
bands are in most cases very irregular, as is shown in 
v. Wright’s two figures of Scandinavian specimens 
(Plate XV, figs. 7 and 9), and in a colour-variety com- 
mon in the Arctic regions, the transverse bands are 
interrupted at the middle of the sides and their superior 
and inferior parts are set alternately opposite the spaces 
between them, a dark band from the back lying verti- 
cally above a lighter band from the anal side and vice 
versa. The belly itself, on the other hand, is usually 
of a uniform gray or red, dotted with brown. In Cy- 
clogaster Fabricii the black peritoneum generally shines 
through. Lepechin’s specific name ( lineatus ) is derived 
from a variation of colour common in this species too, 
where the markings of the body are arranged in longi- 
tudinal, undulating streaks. In short, we may find 
every conceivable variation and transition between uni- 
coloured, dotted, spotted and streaked forms, light or 
dark, reddish or grayish, yellow or even blue varieties. 
Collett, indeed, gives ten of these different forms. As 
in the preceding species, however, these variations of 
colour belong chiefly to the younger specimens. The 
variety remarked by Malm ( stellatus ), with star-shaped 
chromatophores in the skin, is also marked (Plate XV, 
fig. 10) by a St. Andrew’s cross of sepia-coloured streaks 
from the eye. This marking is partly represented in 
one of v. Wright’s two figures, and may also occur, 
according to Hansson, in the preceding species. 
The Common Sea-Snail is of especial interest in 
the geology of Scandinavia and Finland during the pe- 
riod immediately preceding that known by geologists 
as the Recent or Human. Its occurrence in the Baltic 
is one of the relics collected b}^ S. Loven, of the qua- 
ternary, northern connexion between this sea and the 
Arctic Ocean. The species has received greatest pro- 
minence from Ekstrom’s description of it, under the 
name of Liparis barbatus a , as occurring in the island- 
belt of Morko, where he found specimens 130 mm. 
long. Far up in the Gulf of Bothnia, too, this species 
attains a length of at least 90 mm., for one of the 
specimens in the Royal Museum 6 , which was taken by 
o 
Mr. Abom off Neder-Kalix, is 94 mm. long. According 
O O 
o 
to Mela it occurs both in the island-belt of Abo and 
off the island of Hogland in the Gulf of Finland. 
Lindstrom assigns it to Gothland, and has presented 
to the Royal Museum a male 60 mm. long, from the 
neighbourhood of Visby. In the south of the Baltic, 
however, it was unknown until Theel and Trybom 
during the voyage of the gunbout Gunhild, in July, 
1878, took a small specimen 19 mm. long, south of 
Ystad, and some other small specimens, the largest of 
which was 26 mm. long, between Moen and Arcona. 
All these last specimens were found at a depth of 10 
or 11 fathoms, among stones and sea- weed on a sandy 
bottom. Off Kiel it does not occur, according to Mo- 
“ This specific name is derived from the beard-like lower lobe of the pectoral fins, and as early as 1785 Bloch had given the spe- 
cies the name of Der Bartjisch, Cyclopterus pinna pectorali barbifovmi. 
b A female with almost ripe roe, taken at the end of April (1842). 
Scandinavian Fishes. 
37 
