948 
SCANDINAVIAN FISHES. 
gituclinal bridge thereof running under the frontal suture 
from the anterior extremity of the triangular squamosal 
(upper) part of the occipital bone forward to the trans- 
verse epiphyseal bridge of cartilage. In front of the 
latter bridge too the cartilaginous roof under the frontal 
bones is wanting above the olfactory lobes; but further 
forward, above the orbitosphenoid bone (obsp), begins 
the compact ethmoidal cartilage, extending forward to 
the tip of the snout. The last-mentioned cartilage, with 
its two terete transverse processes on each side, one in 
front of ( pcna ) and one behind ( pcnp ) the nasal cavity, 
resembles that of the Salmons; but it rises anteriorly 
in a carina, and its covering bones, the true ethmoid 
bones, the vomer, and the lateral ethmoid bones ( etl ) are 
more developed. The ethmoid bones proper extend over 
the anterior transverse process of the cartilage {pcna, 
the palatine process, on which the anterior extremities 
of the palatines and, partly, of the maxillaries have 
their articular surfaces), and each of them sends out 
backwards, on the upper surface of the cartilage, below 
and between the frontal bones, a long process, extend- 
ing to about a line with the middle of the orbits. The 
lateral ethmoid bones (etl), covering the hind transverse 
process (pcnp) of the ethmoidal cartilage, spread like 
wings on either side. The vomer ( vorn ) is narrow and 
long, being pointed behind and somewhat longer than 
the upper ethmoid bones. The parasphenoid bone (psp) 
is principally characterized by its complete division into 
two vertical plates behind the orbits, under the petrosal 
bone (the bone round goa, os prooticum) and the basilar 
part ( ocb ) of the occipital bone, and by its great elonga- 
tion in a backward direction, where it projects beyond 
the last-mentioned bone. In the Salmons Ave found, it 
is true, that the hind orbito-muscular canal Avas rather 
large and open behind; but here the canal is still larger 
and entirely open, even beloAv, its sides being formed by 
the vertical posterior plates of the parasphenoid bone 
and correspondent lamelliform processes descending from 
the petrosal and occipital bones, Avhich in their turn 
form the roof of the canal (see tig. 237, C). 
As the temporal aperture is a characteristic of the 
upper part of the cranium in the Clupeoids, so Ave find 
beloAv a large and characteristic foramen (fen), covered 
only by the mucous membrane of the branchial cavity 
(upper pharynx). It occupies the point Avhere the pet- 
rosal bone and the basilar and lateral ( ocl ) parts of the 
occipital bone Avould otherAvise meet, and is separated 
by a special osseous septum (the bone round gop) from 
the foramen behind it (in the lateral part of the occi- 
pital bone), through Avhich the nervas vagus passes out 
of the cerebral cavity. Hassk" explains this foramen 
(fen) as “the first appearance in the animal kingdom of 
that most important organ, the vestibular AvindoAv” (fene- 
stra ovalis), the communication between the vestibule 
and the tympanic cavity in the higher animals; and on 
the inner side thereof lies the sacculus, belonging to the 
nervous labyrinth, Avith the large otolith. The difference 
from the Salmonoids stands out most sharply on a com- 
parison of this part of the Clupeoid cranium Avith the 
analogous part in the Smelt for example, Avhere the 
foramen is replaced on the under side of the cranium 
by a large swelling, including the sacculus, and formed 
by the above-mentioned bones. 
In the bones surrounding the auditory apparatus of 
the Herring avc meet, hoAvever, Avith an appendage of 
which there is no vestige in the Salmonoids, but Avhich 
is probably analogous to the several lymphatic chambers 
in the neighbourhood of the labyrinth that have been 
noticed in the skull and the front of the spinal canal 
of the Cyprinoids, and Avhich there communicate Avith 
processes of the air-bladder. This appendage consists, 
on each side of the skull, of three osseous globules (goa, 
gos, and gop), filled with air and lined Avith a thin, sil- 
very membrane. Their structure is more compact than 
that of the neighbouring bones, and their Avhite colour 
renders them easily distinguishable. They all lie in 
different planes, one above another; but from the loAver 
posterior globule (gop) runs an osseous duct, which rami- 
fies and sends out a branch to each of the other tAvo. 
The foremost and largest of these globules (goa) lies in the pet- 
rosal bone, just behind the passage for the nervus trigeminus (ftr), 
in the lateral part of the cranial floor, where the said bone sends out 
its leaf-shaped process, down towards the parasphenoid bone, to share 
in the structure of the side-wall bounding the anterior part of the hind 
orbito-muscular canal. The outer posterior, uppermost globule (gos), 
which is skirted by the horizontal (outer), semicircular canal of the 
labyrinth, lies in the squamosal bone, just within the hind part of the 
articular cavity for the hyomandibular bone and outside the opisthotic 
bone (st, os opisthoticum or intercdlare ) . The lower posterior globule (gop), 
the smallest and most elongated (clavate), is situated in the lateral part 
of the occipital bone, between the foramen of the nervus vagus (fv) 
and the fenestra ovalis (fen), forming the very osseous septum between 
these holes that has just been mentioned. The osseous shells of these 
globules and its cavity are indeed continuous; but whether the cavity 
of the membranous lining (sac) also affords at all times a free com- 
munication between them, is a question which we must leave open, 
for in one specimen we have succeeded in preparing the sac of the 
lower posterior globule whole and, as far as we could see, without 
any opening in front. The anterior globule (goa, the petrosal globule) 
Anat. Stud., Bd. I, p. 600. 
