ARCTIC SCOPELUS. 
943 
the preceding species, being almost entirely contiguous 
when the mouth and gill-openings are closed, the only 
space between them then consisting of a lanceolate gap 
at the extreme front, just behind the symphysis. 
The dentition of the mouth and pharynx is weaker 
than in the preceding species, otherwise of similar type. 
The preoperculum is vertically set, slightly curved, with 
the hind margin expanded but extremely thin. The 
operculum, which is half free at the upper margin, is 
quadrangular with rounded corners and smaller than 
the suboperculum, which lies below and inside it; but 
these bones, as well as the interoperculum, are so thin 
and so densely covered with large scales that it is diffi- 
cult to determine the' limits between them and their 
shape without damaging the solitary specimen at our 
disposal. The branchiostegal membranes, with their 8 
rays, are united to each other below and in front, but 
only for a very short distance, to a line with the centre 
of the eyes. The pseudobranchise are distinct and re- 
gular. The gill-rakers resemble those of the preceding 
species, and number 16 or 17 in the outer row on the 
first branchial arch. The last branchial arch of this 
species too is mostly coalescent with the clavicular arch, 
the hindmost gill-slit being consequently very small. 
In contradistinction to the preceding species, the 
Arctic Scopelus belongs to a subdivision of the genus, 
proposed by Gunther, in which the dorsal tin is shorter 
than the anal. The former fin begins half-way along 
the body minus the caudal fin, at a distance from the 
tip of the snout measuring about 51 % a of the length 
of the body excluding the caudal fin. Its base measures 
about 15 % h of the same length. Its first three rays 
are simple; the first two unarticulated. According to 
Kroyer’s figure the fourth or fifth ray is the longest, 
the posterior rays uniformly decreasing in length. The 
adipose fin lies about half-way between the dorsal and 
caudal fins, is broader (longer at the base) than in the 
preceding species, and is supported by fine fibrils (flex- 
ible, corneous rods) within it. The anal fin begins at 
a distance from the tip of the snout measuring about 
“ Answering to 41 / in the preceding species. 
b Answering to 30 % in the preceding species. 
c Answering to about 59 % in the preceding species. 
d Answering to about 22 % in the preceding species. 
e Answering to 7 — 8 % in the preceding species. 
f Answering to nearly 10 / in the preceding species. 
9 In the preceding species about twice this breadth. 
h Answering to nearly 1 3 % in the preceding species. 
i Answering to about 13 G % in the preceding species. 
j Answering to nearly 18 % in the preceding species. 
547 2 % c of the length of the body excluding the caudal 
fin, and its length is about 24 % d of the same. The 
first two rays are simple and unarticulated, the first 
ray being very small. The branched rays, accordingly 
to Kroyer’s figure, decrease uniformly and slowly in 
length behind. The shape of the caudal fin cannot be 
ascertained from our specimen; but the fin has certainly 
been deeply forked, and the length of its middle rays, 
here as well as in the preceding species, differs but 
little from the interorbital width, being nearly 67a 
of' the length of the body excluding the caudal fin. In 
our specimen we find 8 supporting (spinous) rays at the 
upper margin of the caudal fin and 6 at the lower. 
The pectoral fins, which are set obliquely and rather 
high, are narrow, but very long, measuring 18 % f of 
the length of the body excluding the caudal fin. The 
ventral fins, which lie rather near each other, the di- 
stance between them being scarcely equal to the breadth 
of the base of either fin 6 ', are shorter than in the pre- 
ceding species. Their length is 7 k/ °f that of the body 
excluding the caudal fin. Their distance from the tip 
of the snout, here as in the preceding species, is about 
2 / 5 of the length of the body excluding the caudal fin. 
The distance between them and the foremost point of 
the base of the pectoral fins (the preabdominal length) 
is 7 9 \ and that between them and the beginning of 
the anal fin (the postabdominal length) about 15 % j , 
of the length of the body excluding the caudal fin. 
The shortening of the body in this species, as opposed 
to the preceding one, thus affects in the most essential 
degree the abdominal region. 
The scales are comparatively larger than in the 
preceding species, but equally thin and of essentially 
the same shape and texture. The greatest difference 
meets us in the scales of the lateral line, which are 
considerably higher (broader). A scale from the middle 
of the lateral line in our specimen is 2’1 mm. long and 
5'3 mm. broad. Its anterior (inserted) margin is rather 
evenly rounded (not triangularly pointed at the middle, 
as in the preceding species), with only faint sinuses, and 
Scandinavian Fishes. 
119 
