948 



SCAXDIXAVI.W FISHES. 



,iritudiiiiil hridgo thereof ruiiaiiig under the frontal suture 

 from the anterior extremity of the triangular squaniosal 

 (upper) part of the occipital bone forward to the trans- 

 verse epiphyseal bridge of cartilage. In front of the 

 latter bridge too the cartihiginous roof under the frontal 

 l)ones is wanting above the olfactory lobes; but further 

 forward, above the orbitosphenoid bone (obsj)), begins 

 the couipaet ethmoidal cartilage, extending f()r\^ar(l tn 

 tlie tip of the snout. The last-mentioned cartilage, \\ith 

 its two terete transverse ])rocesses on each side, one in 

 front of {^icna) and one behind {pcnp) the nasal cavity, 

 resembles that of the Salmons; but it rises anteriorly 

 in a carina, and its covering liones, tlie true ethmoid 

 bones, tiie vomer, and tlie lateral etinuoid bones (i'tl) 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 tlie palatines and, jiarth", of tiie maxillaries have 

 tlieir articular surfaces), and each of them sends out 

 backwards, on the upper surface of the cartilage, below 

 and between the frontal bones, a long ])rocess, extend- 

 ing to about a line with tlie middle of the orbits. The 

 lateral ethmoid lioiies (cfl), covering the hind transverse 

 process {pcnp) of the ethmoidal cartilage, spread like 

 wings on either side. The vomer (vom) is narrow and 

 long, being pointed behind and somewhat longei- than 

 the upper ethmoid liones. The parasphenoid bone (psp) 

 is i)riiicipally characterized by its coiuplete division into 

 two vertical plates behind the orbits, under the jietrosal 

 bone (the bone round goa, as prooticum) and the basilar 

 part (och) of the occijiital bone, and liv its great elonga- 

 tion in a backward direction, where it projects beyond 

 the last-mentioned bone. In the Salmons we found, it 

 is true, tliat the hind orbito-muscular canal -was rather 

 large and open behind; but here the canal is still larger 

 and entii'ely open, even below, its sides being formed liy 

 the vertical posterior plates of the parasphenoid bone 

 and coi'respondent lamelliforin processes descending from 

 the ])etrosal and occi])ital bones, \vhich in their turn 

 form the roof of the canal (see tig. 237, C). 



As the temporal ajierture is a characteristic of tlie 

 upper part of the cranium in the Clupeoids, so we find 

 below a large and characteristic foramen (fen), covered 

 only by the mucous membrane of the branchial cavity 

 (upper pharynx). It occupies the point where the pet- 

 rosal bone and the basilar and lateral {od) parts of the 

 occipital bone would otherwise meet, and is separated 

 » Anat. Stud., Bd. I, p. GOO. 



by a s]iecial osseous sejjtum (the bone round fiop) from 

 the foramen behind it (in the lateral jiart of the occi- 

 pital bone), through which the iierrus vagus passes out 

 of the cerebral cavity. Hasse" explains this foramen 

 (fcit) as "tlie tirst ai>pearance in the animal kingdom of 

 that most inijjortant organ, the vestibular window" (fene- 

 stra oralis), the communication between the vestibule 

 and the tvmpanic ca\it\- in the higher animals; and on 

 tlie inner side thereof lies the sdiridiis, belonging to the 

 nervous labvrintli, with the large otolith. The difference 

 from the Salmonoids stands out most sharply on a com- 

 parison of this part of the Clupeoid cranium with the 

 analogous ])ai't in the Smelt for example, -where the 

 foramen is rcjilaced on the under side of the cranium 

 l)y a large swelling, including the sacciihis. and formed 

 by the above-mentioned bones. 



In the bones surrounding the auditory apparatus of 

 the Herring we meet, however, with an apjiendage of 

 which there is no vestige in the Salmonoids, but which 

 is probably analogous to the several lym])hatic chambers 

 in the neighbourhood of the ]al)\riiitli tliat have been 

 noticed in the skull and the front of tlie spinal canal 

 of the Cyprinoids, and \vliich there communicate ^\•ith 

 processes of the air-bladder. This appendage consists, 

 on each side of the skull, of three osseous globules (goa, 

 gos, and goji), tilled with air and lined with a thin, sil- 

 verv membrane. Their structure is more comjiact than 

 that of the neighbouring l)ones, and their white colour 

 renders them easilj' distinguishable. They all lie in 

 different planes, one above another; but from the lower 

 posterior globule {gop) runs an osseous duct, which rami- 

 fies and sends out a branch to each of the other two. 



The foremost and largest of these globules (ijoa) lies in tlie pet- 

 rosal bone, just behind the passage for the nevviis 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-nuiscular canal. The outer posterior, uppermost globule (i/os), 

 whicli is skirted by the horizontal (outer), semicircular canal of the' 

 labyrinth, lies in the squamosal bone, just within the hind part of (htf 

 articular cavity for the hyomandibular bone and outside the opisthotic 

 bone {st, os opisthoticum or intercalare). The lower posterior globule Q/op), 

 the smallest and most elongated (clavate), is situated in the lateral part 

 of the occipital bone, between the foi-amcn of the nervus vayus (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 w-e could see, witliout 

 any opening in front. The anterior globule (ijoa, the petrosal glolmle) 



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