ROUSSETTES. 
1151 
dorsal margin as from the ventral, but on the tail at 
about the middle of the sides, until it reaches the an- 
terior part of the caudal fin, where it bends down- 
wards in a loop to the lower third of the depth of 
the body. 
The Black-mouthed Dog-fish is most known in the 
Mediterranean and on the coasts of Portugal and Nor- 
way, this being probably due to the circumstances that 
it generally lives at a depth of about 100 — 250 fthrns., 
and that fisheries at this depth are most developed in 
the said localities. But it also roves into higher strata, 
being met with, though seldom, in the North Sea, and 
penetrating in the Skager Rack and Cattegat into 40 
fathoms of water (Malm) off Bohusl&n and in Christia- 
nia Fjord, or even, as once happened, in March, 1847, 
according to Nilsson, into the Sound off Raa. Lowe 
has described it from Madeira; according to Collett 
it has been found off’ Tromso. It thus has a wide 
geographical range in the North Atlantic. 
The food of the Black-mouthed Dog-fish consists 
of fish and crustaceans. It takes the ordinary bait of 
deep-sea lines. During spring and summer the female 
deposits her singular eggs (fig. 333), two at a time, 
as described by Gunnerus. The life of this species is 
otherwise little known ; but where it is taken in any 
number, the flesh is considered eatable. 
Genus SCYLLIORHINUS". 
Nostrils approximated behind to the month or even meeting the anterior margin of the upper jaw , the distance 
between which margin and the tip of the snout is less than the post orbital length of the head. Upper edge of 
the caudal fin without prominent serrations. 
As has been hinted above, the difference from the 
preceding genus is rather inconsiderable. The most 
important distinction consists in the advancement of the 
mouth and the more or less marked prolongation of the 
nostrils back towards the mouth cavity. Consequently 
we also find in the genus Scylliorhinus that the tip of 
the lower jaw is in a line with or even in front of the 
preorbital margin. The genus is indeed without serra- 
tions at the upper edge of the caudal fin , though these 
may sometimes be traced in the difference between the 
large spiny scales in the upper rows on each side and 
the smaller and smoother ones in the median dorsal 
line at the said spot; but it has a compensation for 
them in the stronger development of the spiny scales 
on each side of the body above and behind the anal 
fin, which almost exactly resemble jaw-teeth. These 
scales literally form a rasp, which the fish uses as a 
defensive weapon. 
To the characteristics of the genus also belongs 
the form of the egg-capsules (fig. 335). These are 
similar to those of the Rays, oblong, rectangular, and 
flattened, but with one half thicker than the other. 
At each corner they are furnished with a long (mea- 
suring sometimes half a metre) filamentous appendage. 
When the first pair of these tendrils emerge from the 
cloaca, the female coils them round a branch of sea- 
weed or coral, where the egg is left hanging. Two 
eggs, as a rule, become simultaneously ripe for exclu- 
sion, one in each uterus; and the female deposits them 
Fig. 335. Egg of Nurse Hound ( Scylliorhinus stellaris ), cut open to 
show the enclosed foetus, and with the posterior (the first excluded) 
end turned downwards. Nat. size. After Moreau, who further states 
that the ova of this species differ from those of the Rough Hound 
in that the thickened side-margins are transversely striped. 
a 2'/dhov in Aristotle, elsewhere G'/xXaS, ( canicula in Gaza), = whelp. 
145 
Scandinavian Fishes. 
