950 
SCANDINAVIAN FISHES. 
By means of these globules and the ducts between 
them the wall of the air-bladder (but not its cavity, at 
least in full-grown Herrings") is connected with the 
perilymphatic spaces surrounding the auditory apparatus, 
and variations of pressure may thus be transmitted from 
the former to the latter. The connexion is, however, 
comparatively simple, simpler at all events than in the 
Cyprinoids, and, as we have mentioned above (p. 826), 
this structure in the Clupeoids has consequently been 
regarded from a morphological point of view as a pri- 
mitive stage of development of the corresponding appa- 
ratus in the Carp-fishes. Another characteristic of the 
Clupeoids is the connexion of the air-bladder not only 
with the stomach, into whose posterior, pointed extre- 
mity the pneumatic duct opens in the Herring, but also 
A 
Fig. 238. Left scapular arch and pectoral fin of a Herring. 
behind the vent, may help us to explain the circum- 
stance that the air-bladder is sometimes found filled to 
distension with water 0 . 
The structure of the mouth is essentially the same 
as in the Gwyniads. The shape and position of the 
inter m ax illaries in particular show striking similarities 
between the Herring and the Vendace. Here, however, 
these bones are not applied so closely to the maxillaries, 
which are distinguished by the accession of a further 
supplementary bone, situated in front of and (partly) 
outside the posterior one, which, as well as the maxillary 
itself, resembles in shape and position that of the 
Gwyniads. 
Among the remaining peculiarities of the skeleton 
we will only touch upon the shoulder-girdle, which has 
p t -\ 
Natural size. A, from within ; B, from without. 
pt, posttemporal bone; scl, supraclavicular bone; cl, clavicle; clp, ascending process from the anterior margin of the clavicle; sc, scapula; 
cr, coracoid bone; per, prrecoracoid bone; pcl x — 3 , the several postclavicular bones; br, brachial bones (inner row); bre, outer (distal) row 
of brachials. 
with the surrounding water, the hind part of the air- 
bladder being continued by a duct which opens on the 
posterior side of the triangular dermal flap forming a 
prolongation of the hind margin of the anal aperture * * 6 . 
The connexions of the air-bladder with the nearest en- 
vironments of the labyrinth, and the large temporal 
aperture, which interposes only a thin and soft wall be- 
tween those environments and the surrounding water, 
may well be the cause of the sensitiveness to noise so 
highly characteristic of the Clupeoids. The communi- 
cation with the surrounding water, through the opening 
a That the globules and ducts are excrescences of the air-bla 
than probable; but we know of no direct observation on this head. 
6 Cf. Weber, De aure et auditu, p. 73; Bennett, Journ. An 
vol. VI (1883, Jan.), p. 24. 
c Cf. Guv., Val., 1. c., tom. XX, p. 70. 
d Shoulder-Girdle and Sternum, Roy Soc. 1868, p. 57. 
guided Parker 1 * to some morphological conclusions 
highly worthy of attention. The postclavicle is not only 
divided, as in the Salmon, into a row of separate bones 
(in the Herring three, tig. 238, B, pcl t , 3 ), but also 
situated outside the clavicle (cl), an arrangement known 
only in the Herrings. How closely the shoulder-girdle 
of the Herring is connected with the dermal growths, 
a, sign of its primitive rank from a morphological point 
of view (cf. above, p. 635), further appears both in the 
thin, squamoid texture of the upper postclavicular bones 
at the hind margin, and in the still more squamoid, 
ler and in an embryonic state freely communicate therewith, seems more 
Physiol., vol. XIV (1879 — 80), p. 405; Day, The Zoologist, ser. 3, 
