HERRING-FISHES. 
947 
cartilaginous fishes, representing different stages of re- 
duction. Boas'* followed the same method with the 
Teleosts, showing that in Butirinus there is a distinct 
rudiment of a conus arteriosus , with transversely 
striped muscles and two rows of valvules, and that in 
Osteoglossum — now the type of a separate family of 
hard-scaled fishes which in other respects come near to 
the Herrings — and Notopterus — belonging to a family 
also nearly related to the Herrings, but with scaly 
head and without oviducts — the said rudiment is con- 
siderably smaller and possesses only one row of val- 
vules, answering to the front row in the previous fishes. 
In the true Herrings the rudiment has almost entirely 
disappeared, and is replaced merely by a layer of con- 
nective tissue, without striped muscles; and this, as 
we have already mentioned, is the typical condition 
in the Teleosts. 
The essential resemblances between the skeleton 
of the Herrings and that of the Salmons were remarked 
by L. Agassiz. But in the former the skeleton is, as 
a rule, more firmly ossified, and shows some remark- 
able peculiarities in systematic and morphological re- 
spects. 
From a comparison between the skeleton of a Ven- 
dace and that of a common Herring, it appears that 
the same looseness prevails in the union of the lateral 
parts both of the neural arches belonging to most of 
the anterior abdominal vertebral and the haemal arches 
of the posterior abdominal vertebrae. The latter are 
indeed closed throughout a considerable part of the 
trunk, an osseous bridge joining the right shaft of the 
arch to the left; but lower down the shafts again se- 
parate, and the ribs are attached to each part of these 
divided haemal spines. The vertebrae of the Herring 
are further marked — as anyone who lias eaten a Her- 
ring knows — by the number of scleral bones deve- 
loped in the tendinous walls (aponeurotic septa) between 
the transverse divisions (myocommata) of the great 
lateral muscles. A perfect abdominal vertebra (fig. 236) 
has no less than three pairs of such bones, the first 
(na = epineural bones) attached to the base of the neural 
arch or at the limit between that arch and the body 
of the vertebra, the second (pa ----- epicentral bones) to 
the body of the vertebra, and the third (pta — epipleural 
bones) to the base of the ribs or at their insertion. In 
the Salmonoids we find only one or two pairs of these 
scleral bones, the uppermost alone or in association with 
the lowest. In most Clupeoid forms the lower extre- 
mities of the ribs in general are applied to the inner 
surface of osseous growths from the skin, to which they 
are, however, but loosely united. These growths belong, 
as we have seen above in the case of the Sternopty- 
choids, to the median scales of the carinated ventral mar- 
gin, the so-called ventral plates, with their spiniform 
processes in a backward direction (dh). 
In the Herring too a great part of the chondro- 
cranium is continuous. The long frontal bones (fig. 237, 
fr) send out obliquely backwards and downwards, on 
each side behind the orbits, a large process, which runs 
into the squamosal bone ( squ and gos in the figure, os 
pteroticum ), while the frontal bone itself behind touches 
the parietal bone (par). Between the said three bones 
on each side of the head the cranial wall is pierced by 
Fig. 236. Abdominal vertebra of a Herring. After Brandt and Rat- 
zeburg. ns, upper spinal process (neural spine); n, upper (neural) 
arch; c, corpus; p, transverse process; pi, rib; na, upper extracostal ; 
pa, middle extracostal; pla, lower extracostal; dh, spiniferous plate 
at the ventral margin. 
the large and oblong temporal aperture (ap) b charac- 
teristic of the Herrings. This aperture lies in front of 
the mastoid groove (temporal cavity), which is rather 
large in these fishes as well as in the Salmons and Carps, 
its bottom being composed of the squamosal bone, car- 
tilage, and the mastoid bone (mi in the figure, os epio- 
ticum), while its walls belong partly to these bones, 
partly to the lateral portions of the squamosal part of 
the occipital bone (ocs). It is besides furnished with a 
roof formed by a backward process from the parietal 
bone (par), meeting a forward process from the mastoid 
bone (mt). The greater part of the roof of the cranial 
cavity has lost its cartilage in the Herring, only a lon- 
“ Vid. Meddel. Naturh. For. Kbhvn, 1879 — BO, p. 333. 
6 The temporal aperture sometimes occurs, it is true, in the Salmon (cf. Bruch, Osteol. Rheinlachs, tab. IV, fig. 3, between 0 and z/), and 
appears in the Smelt as a vestige of the great frontal fontanel in the cartilaginous cranium of young fishes. But it is there covered by the frontal bone. 
