1150 
SCANDINAVIAN FISHES. 
The head occupies about, 17 (17 1 / 2 ) — 15 (14'8) % 
of the length of the body, and differs essentially from 
that of the following genus in the length of the snout, 
which measures nearly half (49 1 / 2 — 46 %) of that of 
the head. The snout is translucent, and its skin is 
pierced with numerous ampullar orilices, arranged above 
in series so as to form oblong patches on each side of 
the median line, below in the manner illustrated in 
fig. 334. The nostrils, which are directed obliquely 
inwards and backwards from the edge of the snout, 
have the anterior overlapping margin double (cf. above, 
on the Tope), and the outer lobe (lae) has a pointed 
triangular flap, the base of which is continued inwards, 
the inner ( lai ) an obtuse, more or less rounded flap, 
belonging to the outer part of the nostril. Exactly 
opposite the last-mentioned flap there projects a more 
deep-seated, more tubercular lobe (Ipe) from the pos- 
terior margin of the nostril. In this manner the nostril 
is incompletely divided, as that of the Rays, into an 
outer (anterior) and an inner (a posterior) part; but 
the latter is not confluent either with the nostril of 
the opposite side or with the mouth. The distance 
between the inner ends of the two nostrils is somewhat 
more than 1 / 3 (in the younger among our specimens 
about 36 %, in the older about 34 1 / a %) of the length 
of the snout; and the distance from either of these 
ends to the mouth varies between % and 3 / i of the 
former distance. The orbits are oblong, the vertical 
diameter being about 2 / 5 of the longitudinal or even 
less, and the longitudinal diameter measuring about 
half the length of the snout, somewhat more or less, 
or about 2 / s of the interorbital width. Exactly behind 
the orbits — at a distance from them rather greater 
than their length — lie the spiracles, whose diameter 
is about 1 / 4 of that of the former. The mouth is semi- 
circular, the lower jaw being somewhat more pointed 
than the upper, and is so situated that the anterior 
margin of the upper jaw lies in a line with the pre- 
orbital margin or a little behind the perpendicular there- 
from, the tip of the lower jaw almost beloAv the centre 
of the eyes. Lips are wanting, but the corners of the 
mouth are elevated and posteriorly bounded by a rather 
deep semicircular groove. The teeth are pointed, with 
one or two lateral denticulations on each side of the 
main cusp. They are set in a quincunx of three — five 
series, which gives them the appearance of being dis- 
tributed in some thirty longitudinal rows running 
obliquely backwards and outwards across the jaws. The 
tongue is fleshy and flat, as in most of the Sharks. 
The gill-openings are middle-sized, the hindmost being 
set above the beginning of the pectoral fin. 
The dorsal fins are characterized, as in the follow- 
ing genus, by their similarity to each other both in 
form and size; but in these fins, as in the other un- 
paired fins, it should be observed that the forward 
extension of the anterior margin varies in different in- 
dividuals, the measurement of the basal length being 
thus rendered uncertain. The distance from the tip of 
the snout to the first dorsal fin is about 45 (44 l / 2 — 
47 7$) %, to the second about 63 (62 — 64) %, of the 
length of the body; the interval between the two fins 
measures between 13 and 14 % of the said length. 
Their form is obliquely quadrilateral, with the posterior 
corner almost rectangular. The length of their base 
varies between 4 and 4V 2 % (sometimes nearly 5 %), 
and their height between 5 and 6 1 / 2 %, of the length 
of the body. The first dorsal fin lies opposite to the 
anterior part of the space between the ventral and anal 
fins, the second to the posterior part of the anal fin. 
The last- mentioned fin, which has an unmistakable re- 
semblance to the anterior part of the lower caudal lobe 
(an obliquely trapezoidal form, gradually attenuated 
behind, with pointed infero-posterior corner and slightly 
concave under margin), is here distinguished by its 
length — about 15 — 16 % of that of the body, and in 
the females 4 times or less, in the males up to 5 times 
the greatest height of the fin. The distance between 
the tip of the snout and the beginning of the anal fin 
measures in full grown females perceptibly more than 
v 2 (about 54 %), in males and young females about 
7 2 or less (49 — 51 %), of the length of the body. The 
caudal fin is expanded at the end, obliquely truncate, 
with somewhat rounded corners. Its length from the 
beginning of the anterior lobe is more than 1 / i (27 1 / 2 
to nearly 33 %) of the length of the body. 
The pectoral fins are broad, obliquely truncate, 
with rounded corners. Their length at the anterior 
margin varies between 10 and 1 2 1 / 2 %, their base be- 
tween 6 1 / 2 and 8 %, of the length of the body. The 
ventral fins are quadrangular, low but long, with the 
posterior corner pointed. Their base is longer than that 
of the pectorals — in the females about 87 2 %, in the males 
about 9 %, of the length of the body — but their height 
(breadth) is only about x / 3 or 3 / g of the length of the base. 
The lateral line is quite distinct, from the very 
temples, and at first runs about half as far from the 
