282 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
and basioccipital, also enter into the protection of the auditory 
apparatus, and that in Salmo (the only instance apparently observed 
by him) the epiotic does not contain the exterior semicircular canal. 
The cartilage in which the occipital bones develop did not originally 
form part of the auditory case, the passage of the semicircular canal 
through the exoccipital and supraoccipital being secondary, as the 
hollowing vut of the basioccipital for the sacculus certainly is, so 
that the names applied to these parts more truly indicate their origin. 
Parker’s paper on the skull of the salmon,! published later in the — 
same year, states that, contrary to Vrolik’s opinion, the epiotic does 
arise in connection with a semicirenlar canal, and shows also that a 
similar relation occurs in the pterotic, sphenotic, and opisthotic. 
In the Selachvi the auditory capsule is at first quite distinet from 
the rest of the skull, with which it eventually fuses, and throughout 
life remains without connection with the cranial cavity except by the 
foramen for the auditory nerve. It lies at the sides of the skull, 
but does not extend back to the occipital region. In young Teleosts 
the cartilaginous capsule does not extend back as far as the occipital 
region, lying still at the sides. Now all bones formed in this car- 
tilaginous capsule are certainly entitled to be referred to the “‘ otica ” 
group. The anterior portion of this capsule is ossified as the prodtic 
(petrosum), a tract of osteoblasts outside the ampulla of the anterior 
semicircular canal gives origin to the sphenotic (postfrontal), the 
pterotic (squamosal) arises over the ampulla and arch of the external 
canal, the epiotic (occipital externum) over the arch of the posterior 
canal, and the opisthotic (intercalare) over the ampulla of the same 
canal. All these bones lie in the region oceupied by the cartilagin- 
ous auditory capsule, all are mainly what may be called cartilage 
bones,” and all hold a more or less definite relation to the included 
auditory apparatus. 
The terms prootic, sphenotic, pterotic, eprotic and opisthotic, applhed 
respectively to the bones known to German authors as the petrosum, 
postfrontal, squamosal, occipitale externum, and intercalare, are pre- 
terable, as indicating the true relations of these ossifications. 
Sagemehl in his paper on Amia* makes many ingenious and 
1W. K. Parker.—The structure and development of the skull in the Salmon. Phil. Trans,, 
1873, 
2 Gegenbaur’s objections to the pterotic (Ub. das Kopfskelet von Alepocephalus rostratus 
(Risso). Morph. Jahrb, Bd. IV., suppl., 1878,) have been shown above to be groundless. 
3 Ante cit. 
