548 
SCANDINAVIAN FISHES. 
the Fisheries Commission of the United States in the 
same region “outside the 100-fathoms line.’’ 
That the Four-Bearded Rockling is really a deep- 
sea fish, appears from the comparatively large size of 
its eyes; but it is now and then caught on Cod-lines 
and in shallow water, sometimes no more than 8 or 10 
fathoms deep. Its stomach and intestine have been 
found to contain crustaceans (Cum a, Idothea, Ponto- 
poreia, Crangon, Palcemon), Annelids (Polynoe), and mol- 
lusks ( N-ucula ). Its food thus shows that it keeps to 
the bottom and among seaweed. Its spawning-season 
is not known with certainty; but the female, 312 mm. 
long, which has been the original of our figure, was 
taken by Mr. C. A. Hansson off Stromstad in duly, 
1889, and was full of roe, though this was still firm. 
Parnell’s specimen was a female caught in June, and 
with rather more developed ovaries. To judge by these 
two specimens, the spawning-season occurs during sum- 
mer or at the beginning of autumn. 
The habits of the older specimens are but little 
known; but Edward kept five specimens of the fry in 
the Couchia- stage alive in an aquarium for a week. At 
first they were peaceably disposed among themselves, 
but joined in fiercely attacking a Goby that was their 
fellow-prisoner; and when it was dead, they turned upon 
each other. Edward also observed that they never 
raised the first ray of the first dorsal fin, but that, 
when the other fins were at rest, the filamentous rays 
of this fin kept up a continual vibration, which in- 
stantly ceased when the fish was frightened. The rostral 
barbel evidently served as a special organ of touch, and 
could be lengthened or shortened at will. 
THE NORTHERN ROCKLING (sw. nordisica skarlangan). 
ONOS SEPTENTRIONALIS. 
Fig. 130. 
At least 11 barbels: one at each anterior nostril , a pair on the tip of the snout, three, short, lobate ones, the hind- 
most only tuberculate, on each side behind this pair, in the dermal fold that runs forward from the lower pre- 
orbital margin, and one under the chin. Length of the head in adult specimens nearly 25% of that of the body. 
Longitudinal diameter of the eyes in full-grown specimens less than 30 % of the postorbital length of the head, 
this length being about equal to the distance from the tip of the snout to the hind extremity of the maxillary 
bones, but less than the length of the lower jaw, which is more than half that of the head. Ljeast depth of the 
tail less than 30 % of the depth of the body at the beginning of the anal fin. 
Fig. 130. Onos septentrionalis from Floro (Norway). Natural size. Specimen belonging to the Museum of Christiania University. 
R. hr. 7; IJ. 49—53; A. 41—43; P. 15 — 16; V. 7; C. 
28—30. 
Syn. Motella septentrionalis, Coll., Ann., Mag. Nat. Hist., ser. IV, 
vol. XV, p. 82; Forh. Vid. Selsk. Christ. 1874, Tilltegsh., 
p. 117, tab. II; ibid. 1878, No. 4, p. 20; ibid. 1879, No. 
1, p. 68; Id. (Onos), N. Nordli. Exped. , Zoo!., Fiske, p. 
138, tab. IV, figg. 35 et 36; Ltkn (Motella), Vid. Meddel. 
Natuih. For. Kbhvn 1881, p. 234; Storm, N. Vid. Selsk. 
Skr. Trondhj. 1883, p. 36; Coll. (Onos), N. Mag. Naturv. 
Christ., Bd. 29 (1884), p. 86; Lillj., Sv., Norg. Fisk., 
vol. II, p. 172. 
The Northern Rockling is known almost exclusively 
through Collett’s researches, and, up to the present 
at least, only comparatively small specimens have been 
found. The largest specimen known is only 174 mm. 
