1134 
SCANDINAVIAN FISHES. 
openings or about 1 / 7 of the length of the head. The 
cleft of the mouth is horse-shoed. Its breadth is about 
equal to the postorbital length of the head. Both cor- 
ners of the mouth are surrounded by an impressed 
fold of skin and are sharply defined, the distance from 
the tip of the snout to this posterior limit of the lips 
varying between about 2 / s and 3 / 4 (66 — 77 %) of the 
length of the head, and that from the anterior margin 
of the mouth to the same point being about 45 % a of 
the same length. The teeth are set so unevenly in 3 
or 4 rows within one another that their number in 
one of these rows on each side was estimated by Kr0- 
yer at 7, by Muller and Henle at 17, the former 
having only counted the teeth exactly in a line with 
one another, omitting those close to (within) these at 
the intervening spaces. Both the upper and the lower 
jaws are furnished with a thick, but narrow fold (ve- 
lum) behind the rows of teeth, with lobes answering 
to the dentition. The tongue is broad and fleshy, but 
flat. Of the five gill-openings on each side the last 
two are situated above the base of the pectoral fin. 
The two dorsal fins are of rather similar form, 
but differ widely in size. Their form may be described 
as a triangle with the posterior corner raised above the 
base and strongly prolongated. The basal length of 
the second dorsal fin varies between about 63 and 53 % 
of that of the first, and the anterior margin of the 
former measures from about 58 to 48 % of that of the 
latter, which last-mentioned margin increases with age 
from about 8 to d l j 2 % of the length of the body. 
The distance between the first dorsal fin and the tip 
of the snout is about 1 / s (32 — 34 %), that between the 
second dorsal fin and the same point about 2 / 3 (63 — 
67 %), of the length of the body. The anal fin is si- 
milar to the second dorsal, but somewhat smaller 6 and 
situated a little further back'd The caudal fin resem- 
bles in form that of the Blue Shark, but is shorter, 
its length from the beginning of the inferior lobe to 
the extreme tip of the fin decreasing during growth 
from about 24 to 22 1 / 2 % of the length of the body. 
The inferior lobe is so deeply forked that it almost 
seems to consist of two fins, an anterior, prolongated 
forward so as to form a triangular lobe, behind shal- 
low and of almost uniform depth, and a posterior, which 
is triangular, and together with the elongated shallow 
upper caudal lobe, gradually ascending behind, forms 
the extreme tip of the fin. The paired fins are tri- 
angular. The pectorals are of much the same form as 
the dorsals, but the posterior (inner) corner is only 
slightly prolongated. The distance between them and 
the tip of the snout measures about 23 — 22 %, their 
anterior margin about 13 — 15 %, of the length of the 
body. The ventral fins, which surround the anus, have 
the form of almost right-angled triangles with conti- 
guous hypotenuses. These sides, which are about 1 j i 
greater than the others, measure about 6 — 7 % of the 
length of the body. The distance from the beginning 
of the ventral fins to the tip of the snout is about 50 
- — 53 %, to the beginning of the pectoral fins about 
27 — 30 %, of the length of the body. 
The whole skin of the body — with the exception 
of triangular patches behind the cloacal region and 
the dorsal, the anal, and the pectoral fins — the 
surface of the fins, and the cavity of the mouth, are 
finely shagreenecl with small three-spined placoid scales, 
so small that, when stroked from in front, the body 
is smooth and slippery to the touch, but in the oppo- 
site direction feels harsh and rough. 
The external difference of sex is that normal in 
the Sharks. In the young male represented in our 
figure the pterygopodia had not yet grown beyond the 
tips of the ventral fins. 
The back, together with the dorsal and caudal fins 
and the upper surface of the paired fins, is of a steely 
gray, sometimes with a bronze lustre. The ventral 
side is white, sometimes with a nacreous lustre, or 
yellowish. The iris is white, with a narrow ring of 
cupreous lustre round the black pupil. 
The Tope is known from the Atlantic, Pacific, and 
Indian Oceans. In the Atlantic it has been found from 
the Cape of Good Hope to the Orkneys and the neigh- 
bourhood of Bergen. In the Mediterranean and on the 
coasts of France, the south of England, and Ireland, it 
is common. In the North Sea it becomes less frequent 
of occurrence to the north; but even in the Cattegat 
it cannot be described as rare. North of Bergen it has 
never been met with; but in Christiania Fjord and on 
the coast of Bohuslan, as well as in Danish waters, it 
a According to KR0YER sometimes 50. 
b Base about 90 — 91 % of that of the second dorsal; anterior margin about 80 — 86 % of that of the second dorsal. 
c Distance between the second dorsal and the tip of the snout about 98 — 99 % of that between the anal and the same point. 
