994 
SCANDINAVIAN FISHES. 
margin shows an arcuate indentation. Obliquely across 
its surface, from the articular head to the lower pos- 
terior corner, runs a groove, in front of which the 
lower anterior, triangular part of its surface is some- 
what tumid, but smooth. The suboperculum has a 
rounded triangular form, with the hind margin sharply 
curved. The length of its upper margin, which coincides 
with the breadth of the operculum, is about 10 — 12 % 
of the length of the head. The interoperculum is of 
about the same shape as the suboperculum, but much 
smaller. All the opercular bones are very thin. The 
branchiostegal membranes are narrow, hardly perceptible 
at the hind margins of the operculum and suboperculum. 
In front (below) they follow the branches of the lower 
jaw, their breadth being but slightly greater than that 
of these bones or, at the extreme front, less. The 
branchiostegal rays are also comparatively short, gradu- 
ally increasing behind (with the exception of the last 
one) in length and breadth. The anterior are subulate 
and curved, the posterior of more and more uniform 
breadth and sabre-shaped, with obliquely set, terete shaft; 
' 1 1 i ii AuL.’A*' 
Fig. 251. Composite scale from the left side of the inferior caudal 
lobe in an Anchovy 16 cm. long. X 3. 
the longest ones (in the inferior lobe). On each side 
of the fin are set, as in the Clupeoid forms immediately 
preceding the Anchovy, a pair of so-called composite 
scales — much smaller, however, than the largest body- 
scales — one on the superior lobe, the other on the in- 
ferior, and each consisting of a scalpel-shaped dermal 
flap, with diamond-like reticulation, and covered with 
a considerable number (20 — 25) of small scales. These 
are set in imbricated rows, and each of them is marked 
with a row of brownish black pigment-spots (fig. 251). 
The pectoral fins are comparatively short, their 
length being about equal to the height of the dorsal fin 
or a little greater, and are obliquely truncate, their shape 
reminding us strongly of the pectoral fins in those An- 
chovies where the first ray of these fins sIioavs a fila- 
mentous elongation. The ventral fins are also obliquely 
truncate, but much shorter than the pectoral, their length 
being only about 7 7 2 — 7 % of that of the body. The 
position of the ventral fins is such that the distance be- 
tween them and the tip of the snout measures about 
but the hindmost is of a rounded triangular shape, re- 
sembling in form and position a lower suboperculum. 
The nine middle rays are set on the ceratohyoid bone, 
the last two on the epihyoid. 
The distance between the dorsal fin and the tip of 
the snout is about 44 (447 2 ) — 48 %, its height as well 
as its base about 10 — 11 %, of the length of the body. 
The first ray is extremely small, the second about 73 as 
long as the third (the last simple ray), which is slightly 
shorter than the first branched ray. The last ray in 
the fin is scarcely elongated. The distance between the 
anal fin and the tip of the snout is about 60— 63 7 2 0/o i its 
base about 14 %, and its height (the length of the first 
branched ray) about 6 x / 2 — 7 % , of the length of the 
body. It is thus both longer and lower than the dorsal 
fin, and has a more concave outer margin, the la,st ray 
being somewhat elongated. The first of the two simple 
rays at the beginning of the fin is hardly 7 3 as long 
as the second, which is almost equal in length to the 
first branched ray. The caudal fin is deeply forked, 
the length of the middle rays (about 5 — 57 2 % of the 
length of the body) being even less than 7 3 of that of 
Fig. 252. A scale from the left side of an Anchovy 16 cm. long. 
Three times the natural size. 
40 — 44 % of the length of the body, or 90 — 92 % of 
that between the dorsal fin and the same point. The 
preabdominal length is about 18 — 22 %>, and the post- 
abdominal about 20 %, of the length of the body. 
The scales are extremely thin and transparent, ra- 
ther large, but short, and of a quadrangular shape, 
rounded at the corners (fig. 252). Their posterior (free) 
part is as large as the anterior (covered) portion, and 
is also finely striated, the concentric striae being even 
twice as numerous as on the latter. The radiating 
grooves are sharply defined, originating both at the an- 
terior margin and the posterior. The scales of the pec- 
toral fins, and the pointed axillar scales of the ventral 
fins are long, extending respectively 4 / 5 and 3 / 4 of the 
distance along the fins. The basal scales of the dorsal 
and anal fins are about the same as in the Shads. The 
median line of the belly is covered, it is true, with 
ordinary scales; but vestiges of the spiniferous scales 
that appear in the preceding Clupeoid forms may some- 
times be found. These take the shape of linear thicken- 
