LUMP SUCKER. 
295 
dm. deep (thick) weighs nearly 5 kgnn., the roe form- 
ing 080 grin, of this weight. In shape the Lump 
Sucker is one of our most singular fishes, being bulky 
and polygonal, as the Swedish name shows, for by 
sjurygg (Seven-back) is only meant that it has seven 
longitudinal ridges, marked by large, spinous plates, 
on the body, which is scaleless, but rough with small 
spines. One of these ridges runs in the form of a 
cartilaginous hump along the dorsal line behind the 
head, and generally invests the whole of the first dorsal 
fin, being double between the latter and the second 
dorsal fin. Another ridge runs on each side of the 
body from the upper anterior corner of the eye, be- 
tween the posterior nostril and the latter, and then 
advances over the eye, being fairly straight or some- 
what curved above the pectoral fins, and situated at 
the bottom of the upper third of the body or a little 
higher, out along the tail to the base of the caudal 
fin. Another ridge runs fairly parallel to the latter. 
It begins just behind the gill-opening, about half-way 
between its upper corner and the upper angle of the 
pectoral fin, and advances on the abdominal region, 
along the middle of the side, but on the caudal region 
at about the top of the lower third of the tail. The 
lowest ridge runs on each side of the belly itself, which 
during youth, after the formation of this ridge, is flat 
or even concave between the latter and its correspondent 
on the other side of the body — as if this part of the 
belly were a continuation of the ventral disk - — until 
it becomes rounded when the organs of generation reach 
maturity. This lower ridge is generally continued, after 
a short interruption, by a row of small protuberances 
along the base of the anal fin; and a similar row of 
protuberances — or even two — generally appears 
along the base of the second dorsal fin. A row of two 
or three osseous tubercles generally runs back along 
the branchiostegal membrane, below the cheek, from 
the end of the lower jaw. The depth of the body varies 
considerably with the growth of the dorsal hump and 
the greater or less tumidity of the belly; in old males 
it may often rise to about 45 % of the length of the 
body, and in gravid females to more than half the 
latter. This is also true, though in a less degree, of 
the greatest thickness of the body (across the belly), 
which in old specimens varies between about 25 and 
27 % of the length of the body. The least depth of 
the body too, just in front of the caudal fin, generally 
undergoes even relative increase with age. It is usu- 
ally greater in the male than in the female, and varies 
between 8 and 10 % of the length of the body. The 
head is fairly large, generally more so in the males, 
but its relative length decreases with age, varying in 
full-grown specimens between 26 V 2 and 28 % of that 
of the body. The cheeks fall perpendicularly from the 
broad and flat forehead — the breadth of the inter- 
orbital space at the middle of the eyes, in full-grown 
specimens, varies between about 60 and 70 % (58'3 — 
7 1 %) of the length of the head. The abruptly rounded 
snout is short, but its breadth renders it large: its 
point is occupied by the mouth, which is turned some- 
what upwards, and the breadth of which — generally 
greater in the male than in the female — varies be- 
tween about 55 and 65 % of the length of the head. 
Both jaws, with their thick lips project equally far for- 
ward, when the mouth is closed, but when the latter 
is open, the lower jaw proves to be slightly the longer. 
The jaw-teeth are small and pointed, in younger spe- 
cimens forming two or three rows in front only, and 
set in a simple row behind; but in old specimens set 
in cards which grows gradually narrower behind, and 
are broader (contain more rows) in the upper jaw than 
in the lower. The thick tongue and the palate are tooth- 
less; but the pharyngeal bones, both above and beloAv, are 
set with oblong cards of teeth. The nostrils are double, 
both pairs being sometimes raised in a tubular shape, but 
this is the case, as a rule, only with the anterior pair, 
which are the larger, and lie on a level with the middle 
of the eyes, the distance between them and the latter 
being about equal to the diameter of the eye (some- 
what less in young specimens). The eyes are laterally 
set and mobile"; they are situated high up, below the 
margin of the forehead and just in front of the middle 
of the head, in full-grown specimens generally measur- 
ing from about 17 to 22 % of the length of the latter 
— in old specimens from greater depths this proportion 
may rise to 25 %, and in young specimens the eyes 
are, as usual, larger. In young specimens between 24 
and 28 mm. long we have found them to measure as 
much as 36 x / 2 and 31 % of the length of the head. 
The gill-opening begins superiorly on a level with the 
superior margin of the eye, and ends below, in front of 
the base of the pectoral fins, on about a level with the 
mouth. Below this point the thick branchiostegal mem- 
brane hangs like a dermal fold straight across the throat. 
O O 
“ “Je ne connais aucun poisson qui tourne ses yeux brillants avec tant de promptitude”: Ascanius. 
