VENDACE- 
895 
whole iris, but broadest at the anterior corner of the 
eye. The pupil is fairly circular, with only a faint 
angle in front. In adult Vendace the eyes occupy with 
fair exactness the second quarter of the length of the 
head, though the anterior corner of the eye encroaches 
upon the first quarter thereof, the average longitudinal 
diameter of the eye being thus about 25 % a of the 
length of the head, but the length of the snout only 
about 21 V 2 0/0 °f the same. The vertical diameter is 
somewhat less, in albula on an average about 23 % b , in 
vimba 22 x / 2 %, of the length of the head. The breadth 
of the interorbital space, which rises only a little above 
the upper margin of the eyes, is in albula about equal 
to the longitudinal diameter of the eyes c , in vimba 
somewhat greater''. The average breadth of the snout 
across the articular knobs of the maxillaries is 19 % of 
the length of the head. The two nostrils on each side 
of the snout are situated as in the preceding species, 
somewhat nearer to the orbit than to the tip of the 
snout. The hind margin of the anterior nostril is raised 
in the form of an obliquely cut tube; the posterior 
nostril, which is larger, may be closed from in front 
by means of a semicircular dermal flap. The maxillaries 
— as they appear externally — are of uniform breadth, 
curved like a sabre, and bluntly rounded at the hind 
extremity. Their average length from the top of the 
articular processes is in albula about 35 %, in vimba 
about 34 %, of that of the head, or in the former about 
48 %, in the latter about 45 %, of that of the head 
reduced. Their breadth is on an average 1 / 3 of their 
length. Their supplementary (jugal) bone is similar in 
shape to their lateral part and nearly 3 / 4 of its length, 
being elongated to a point in front. The average length 
of the lower jaw is in albula about 51 %, in vimba 
about 49 %, of that of the head, or in the former about 
70 %, in the latter about 66 %, of that of the head re- 
duced. The dentition of the mouth and the gill-rakers 
(41 — 48, exceptionally 39 or even 38) we have already 
noticed. The transverse palatal folds (vela) are well- 
developed, especially in the lower jaw. The gill-open- 
ings extend along about the last third of the upper 
opercular margin and down to about a line with the 
anterior margin of the eye, to which point the bran- 
chiostegal membranes are free both from each other and 
the isthmus, though they cross at the extreme front, 
in the same manner as in the preceding genera. The 
branchiostegal rays are thin and flat, more or less cur- 
ved in a sabre-like form. The operculum is obliquely 
quadrangular, with the lower anterior corner most 
pointed and most elongated. Back from the articular 
process runs a ridge, faintly marked in the bone itself, 
but more distinctly indicated by a darker colour. Within 
the right angle of the preoperculum lies a pore, marked 
by a darker colour, and belonging to the inner osseous 
ridge of the preoperculum, which ridge it pierces, but 
covered by the adipose membrane that here, as usual, 
covers the ramifications of the lateral line. This pore 
is always distinct in Scandinavian Vendace and gene- 
rally in young Gwyniads (as in young Nelma’s); but in 
adult specimens of the larger Coregoni (as in the Nelma) 
it becomes more and more indistinct, usually invisible. 
The dorsal fin is of the shape commonest among 
the Salmonoids, trapezoidal, the first branched ray being 
the longest in the fin. The distance between it and the 
tip of the snoutd is on an average about 43 1 / 2 % of the 
length of the body, usually somewhat greater than in 
the closely allied Siberian form Coregonus Merlcii. The 
base of the fin measures on an average in albula about 
9 %, in vimba about 10 %, of the length of the body, 
and its height (the length of the longest ray) in the 
former about 14%, in the latter about 15 % of the same. 
The anal fin differs but little from the dorsal, but is 
longer and lower, most so in vimba , its base measuring 
on an average about 11 or 12 %, its height about 8 x / 2 
— 9 V 2 0// °i °f the length of the body. Its distance from 
the tip of the snout is on an average 69 by % of the 
length of the body. It terminates, like the adipose fin, 
at a distance from the caudal fin that is on an average 
7 10 of the length of the body. The caudal fin is deeply 
forked, most so in vimba , the average length of the 
middle rays being about 5 1 / 2 — 5 %, of the longest rays 
about 17 — 19 %, of the length of the body. 
The pectoral fins are obliquely pointed, and their 
length is on an average 16 — 15 % of that of the body. 
“ The changes of growth run between about 32 and 23 /. 
h The changes of growth run between about 27 and 20 %. 
e On an average 25‘7 % of the length of the head. 
d On an average 27'7 % of the length of the head. 
e We may remind the reader that here, as in the following Gwyniads, the snout is measured from the articular knob of the maxil- 
lary bone. 
113 
Scandinavian Fishes. 
