BLEAK. 
793 
The length of the head varies between 19 and 21 
% of that of the body, its size being thus somewhat 
below the average among the Scandinavian Cyprinoids. 
It is rather pointed, of uniform thickness, and com- 
pressed, at the top convex, with fairly parallel cheeks. 
The facial line is straight from the occiput to the tip 
of the snout. The breadth of the interorbital space 
measures about 3 / 10 °f the head, and is generally some- 
what greater than the longitudinal diameter of the eyes, 
but sometimes equal to this diameter, which also differs 
only slightly from the length of the snout. The nostrils 
lie on a level with the upper margin of the eyes, 
nearer to the eyes than to the tip of the snout; and 
the distance between the anterior nostrils is equal to 
that between either of them and the middle of the tip 
of the snout. As usual in this family, the two nostrils 
of each side are separated by a narrow dermal ridge, 
raised in a lobate form, and the shape of the nostrils 
varies with the position of this ridge: when it is thrown 
back, the anterior is round, the posterior crescent- 
shaped. The situation of the eyes is such that the 
postorbital length of the head is as a rule somewhat 
less, but sometimes rather more, than half (44 — 52 %) 
of its entire length. The mouth is turned sharply up- 
wards, its entire cleft lying in front of the perpendi- 
cular from the nostrils, which line, when the mouth 
is closed, touches the hind extremity of the maxillary 
bones. A small notch in the sharp tip of the snout, 
which is formed by the intermaxillaries (the margin 
of the upper lip), receives the blunt and rather pro- 
minent point of the lower jaw. The length of the 
upper jaw from the middle of the tip of the snout is 
often almost equal to the length of the snout, measur- 
ing 29 — 26 % of that of the head. The length of the 
lower jaw is 35 — 40 % of that of the head. The gill- 
openings are fairly large, the branchiostegal membranes 
coalescing with the isthmus almost beside each other, 
a little in front of the perpendicular from the hind 
margin of the preoperculum. The gill-rakers are close- 
set: in the outer row on the front of the branchial 
arch (16 or 17 in number) they are slender and wand- 
shaped, while in the inner row on this arch and in 
both rows on the other arches' and on the outer an- 
terior margin of the pharyngeals they are short and 
of a pointed triangular form. The pseudobranchiae are 
well developed. The pharyngeal teeth are distinguished, 
here as in the Rudd, by the pectination of the masti- 
catory surface, at least before it is worn smooth, in 
the case of the three or four posterior teeth in the 
inner row. The two anterior teeth or at least. the first 
tooth in this row, are as usual more conical, the se- 
cond with or without pectinated masticatory surface, 
or with this surface worn smooth. Such is also the 
form of the two small teeth in the outer row. The 
pharyngeal cartilage is oval, with grooves obliquely 
crossing the masticatory surface, as in the majority of 
the Leuciscines described above, and with the hind 
(lower) extremity somewhat raised, a trace of the in- 
verted canaliculate form more highly developed in the 
larger Leuciscines. 
The dorsal fin begins at about the middle of the 
length of the body" or a little further back. It is of 
almost the same trapezoidal form as in the Leuciscines, 
with the length of the last ray at least rather more 
than V 3 of that of the longest ray, which here seems 
hardly to exceed 15 % h of the length of the body. 
The base of the dorsal fin measures about 7 n c of the 
length of the body. The anal fin begins below the 
posterior part of the dorsal L It is long*", low behind, 
and forms a slight arch at the concave inferior mar- 
gin. The first ray is hardly perceptible, the second 
half as long as the third, the fourth the longest/ and, 
like the following rays, branched at the tip. The 
caudal fin is deeply forked, the lower lobe being some- 
what longer than the upper, and measuring somewhat 
more than 1 / 5 of the length of the body. 
The pectoral fins are obliquely and bluntly pointed. 
Their length is about 1 / 6 (16 1 / 2 — 177 2 %) of that of 
the body. The ventral fins are much shorter, measur- 
ing about 12 — 13 % of the length of the body. Their 
position is such that the distance from the tip of the 
snout to their insertion 6 ' does not seem to exceed 
“ At a distance from the tip of the snout measuring 50 — 52 1 /' 2 of the length of the body; the latter percentage in our oldest fe- 
male specimens. 
b Varying, according to our measurements, between 1 3 1 /, and 14 *U #■ 
c According to our measurements 8 ' 7 — 9'7 %. 
d At a distance from the tip of the snout measuring about 59 % ( 57 ' 4 — 59'3 %) of the length of the body. 
e The base of the anal fin measures about 17 % ( 16'4 — 1 7 ' 6 %) of the length of the body. 
f About 11 / ( 11 * 8 — 10'5 %) of the length of the body. 
g 40 — 43 % of the length of the body. 
