HERRING -FISHES. 
951 
leaf-shaped extension of the posterior part of the supra- 
clavicle ( scl ), on which too the posttemporal canal of 
the lateral line is sometimes continued. In the appa- 
ratus of the pectoral tins we find a peculiarity other- 
wise unknown among the Teleosts, but characteristic of 
the Ganoids, namely the outer row (bye) of brachials 
(basal bones of the pectoral fins) possessed by the 
Herring®. 
The organs of respiration are exceedingly well de- 
veloped in the Clupeoids; and they are protected as a 
rule by numerous and long gill-rakers. The pseudo- 
branchne are large, and in many forms'' we find on each 
side a separate, accessory branchial cavity, resting on 
the hindmost (fourth) epibranchial bone, which is flat- 
tened out into a plate for that purpose". 
The digestive organs are as a rule comparatively 
simple, as in the Salmons. In all the Scandinavian 
Herrings the short oesophagus passes without external 
distinction into the stomach, which is prolonged into a 
sac and pointed behind; and from the anterior part of 
this sac issues in a forward direction the more or less 
muscular pyloric portion, bending back quite as sharply 
to pass into the intestine, which is fairly straight and 
runs without any convolutions to the vent. In exotic 
forms however — as for example in the Brazilian Clu- 
pea anchovia — the wall of the pyloric portion is some- 
times thickened, in the same way as in the Mugiloids 
(see above, p. 329), into a sort of ingluvies, and the 
prolongated intestine forms several convolutions. Other 
Clupeoid forms show no backward prolongation of the 
stomach. The pyloric appendages are generally well de- 
veloped, but quite as variable as in the Salmonoids. 
Even among the Scandinavian species the variations in 
the number of ca^cal appendages behind (below) the 
pylorus are very great, the Sprat for example having 
6 — 13, the common Herring 20 — 24, and the Shads 
about 80. In some exotic Clupeoids d the anterior por- 
tion of the intestine (the duodenum), into which the 
pyloric appendages open, is so greatly prolonged that 
bunches of these appendages occur almost throughout 
the length of the abdominal cavity. The mucous mem- 
brane lies, as usual, in longitudinal folds within the 
oesophagus and stomach; but in the intestine the folds, 
which are most developed, among the Scandinavian Clu- 
peoids, in the Shads, are transverse. The liver is gene- 
rally small, sometimes exceedingly small; the spleen 
commonly long and narrow. The saccate organs of 
reproduction ■with their complete excretory ducts are 
so large during the time of propagation that they fill 
the greater part of the abdominal cavity; but at other 
times, as in the generality of fishes, they are contracted, 
sometimes scarcely visible. The connexions of the air- 
bladder we have already mentioned, and we will simply 
add that the pneumatic duct sometimes opens into the 
posterior end of the stomach, sometimes further forward 
or into the oesophagus. In some cases too the wall 
of the air-bladder lies so close to the dorsal side of 
the stomach that the said duct is merely a very short 
funnel. 
The scales are generally thin, deciduous, and cy- 
cloid, smooth-margined, or, not unfrequently, notched or 
even fringed with sharp spines at the hind margin. The 
head is always scaleless, as well as the fins in general; 
but the scales extend rather often over a great part of 
the caudal fin and the base of the dorsal, more rarely 
over that of the anal, and the axillary scales of the 
pectoral and ventral fins are in most cases well developed. 
Especially characteristic of most Herring forms are the 
angular, spinigerous scales at the abdominal margin, 
which send out lateral processes to meet the lower ends 
of most of the ribs (fig. 236, dh; fig. 240, p. 958). 
The system of the lateral line shows great deve- 
lopment, accompanied by a wide extension of the so- 
called adipose membrane, on the head; but the lateral 
line proper is wanting on the sides of the body, with 
the exception that in the common Herring we some- 
times find the first (3 — 5) scales in one of the rows 
pierced in the ordinary manner. In certain forms, as 
for instance the Shads, the lateral line again crops up in 
some scales of singular shape, situated on the caudal fin". 
The fins of the Clupeoids display the same wealth 
of variations as those of the Carp-fishes, and here too 
the variations principally affect the vertical (unpaired) 
fins. The dorsal, which is never very long, sometimes 
suffers reduction to the vanishing point; the anal, on 
the other hand, is sometimes exceedingly long, occa- 
a Cf. Davidoff on the ventral fins of the Cyprinoids; see above p. 718. These bones appear in a cartilaginous form in several other Physostoms. 
6 See Hyrtl, Uber die accessorischen Kiemenorgane der Clupeaceen, Denkschr. Akad. Wiss. Wien, Math. Naturw. Classe, Bd X 
(1885), p. 47. 
c This spreading of the bone may be seen in the common Herring, though the accessory branchial cavity is not present. 
d See Hyktl, 1. c., p. 51. 
e See Heckel und Kner, Susswasserfische der Ostreichisch'en Monarchic, pp. 230, 231. 
Scandinavian Fishes. 
120 
