GREATER SCOPELUS. 
939 
bone. There is no true tongue, but the cartilaginous 
tip of the lingual bone is rather high and prominent 
right in the angle between the branches of the lower 
jaw. Here the hyoid arch of each side is attached, 
and just behind it the first branchial arch, the inferior 
part of which is so long that it extends behind the 
branches of the lower jaw. The anterior gill-slits are 
also very large; but the last (fourth) branchial arch, 
with only one row of lamella?, is united throughout 
the greater part of its length to the shoulder-girdle, 
the hindmost gill-slit thus being quite short and open 
only below. The gill-rakers are setiform. The outer 
row on the first branchial arch contains about 25 gill- 
rakers, 17 of them belong to the lower, front part of 
the arch. The pseudobranchise consist of a longitudinal 
row containing about 22 transversely set, filamentous 
lamella? on the inner, upper surface of the hyomandi- 
bular bone. The opercular apparatus is considerably 
prolongated in a backward direction. The preoperculum, 
which has no lower (forward, horizontal) arm, lies, as 
in the Anchovy, in an oblique, backward and down- 
ward direction. Behind, this bone expands into a thin, 
dermatoid, membranous margin, which lies over the an- 
terior part both of the operculum and the suboperculum, 
and this membranous margin is covered with scales 
pierced by a branch of the lateral line. The shape of 
the quadrangular operculum is adapted to that of the 
preoperculum, the former being also oblique, rhombic, 
and obliquely set, in the same direction as the preoper- 
culum. The hind extremity of the opercular apparatus 
is formed by the upper posterior corner of the trian- 
gular suboperculum, the lower posterior side of which 
is indented, and at the lower angle of which lies the 
small, rounded, and scale-shaped interoperculum. The 
black branchiostegal membrane of each side is entirely 
separate from that of the other side, but is closely ap- 
plied and united by connective tissue to the inner sur- 
face of the branch of the loAver jaw, thus forming, as it 
were, a lining thereof, and hardly projecting beyond its 
margin. The eight slender branchiostegal rays increase 
in length backwards, but are comparatively short. On 
the hyoid arch lie the three luminous spots that shine 
through the branch of the lower jaw, the first at the 
base of the foremost three rays, the second on the space 
between the fifth and sixth rays, and the third on the 
membrane between the bases of the seventh and eighth 
rays. The gill-opening on each side extends upwards 
beyond the superior margin of the operculum, and the 
distance from the tip of the snout to the upper angle 
of each gill-opening is equal to the postorbital length 
of the head. 
The true dorsal fin is rather large and of a quad- 
rangular shape, with undulating upper posterior margin. 
The fin begins at a distance from the tip of the snout 
measuring about 38 % of the length of the body. The 
length of its base is about 28 %, and that of its longest 
ray (the fourth or fifth) about 18 %, of the length of 
the body. The first four rays are simple — the first 
ray, which is very small, also unarticulated. Among 
the remaining rays the anterior (13 or 14) are branched 
only once and at the tip, the posterior (6 or 5) twice 
and more deeply. The adipose fin, which is short but 
rather high, only slightly lower than the hindmost dorsal 
rays, lies about half as far from the dorsal fin as from 
the first upper supporting ray of the caudal. The anal 
fin is similar in shape and structure to the true dorsal, 
but much shorter, with only three simple rays at the 
beginning. The first ray is so small that it easily es- 
capes attention, and the third is the longest in the whole 
fin, or equal in length to the first branched ray. The 
distance between the beginning of the anal tin and the 
tip of the snout is about 54 %, and the base of the fin 
measures about 20 %, of the length of the body, the 
base thus terminating a little behind the perpendicular 
from the adipose fin. The height of the anal fin (the 
length of the third or fourth ray) is about 16 % of the 
length of the body. The caudal fin, which is deeply 
forked, is remarkable in this species too for the short 
but strong supporting rays, true spinous rays, that arm 
the dorsal and ventral margins of the tail in front of 
the true base of the fin. In the only perfect specimen 
within our reach there are both above and below 10 
spinous rays, gradually increasing in length behind, and 
2 articulated but simple rays, the first about one-third 
as long as the second, which extends nearly to the tip 
of the fin-lobe. The remaining 16 rays are articulated 
and branched, the middle ones about one-third as long' 
as the outermost, and measuring about 7 % of the length 
of the body; but the base of the fin is covered at the 
sides, at least half-way along the fin, with elongated 
scales, concealing the roots of the rays. 
Among the paired fins the pectorals are pointed, 
shorter and narrower than the ventrals, which are rounded 
and of average size. The length of the former is about 
9 of the latter nearly 12 of that of the body. 
The first (uppermost) ray in the pectoral fins is simple 
