704 ALLIS, (Vou. XII. 
the skull that lies posterior to the capsule develops, in its dor- 
sal portion, later than, and independently of, that capsule, and 
then fuses with it to form the occipital or postauditory region. 
Whether the skull of these young larvae, that is, that part of 
the skull of the adult that lies anterior to the hind wall of the 
auditory capsule, is the protometameric skull of Sagemehl (No. 
105, p. 527), the equivalent of the skull of adult amphibians 
and selachians, or is equivalent to that skull less the occipital 
vertebra of Stohr, I am unable to judge, not having been able 
to see the particular publication referred to by Sagemehl. My 
work, however, strongly inclines me to accept the assertion 
attributed to Stohr, that a vertebra, lying originally between 
the vagus and first spinal nerves, has fused with the hind end 
of the amphibian skull, and also to consider the skull, as first 
formed in young Amia, as the true protometameric skull of Sage- 
mehl, but as something less than that skull as defined by him. 
The anterior limit of the ventral portion of the postauditory, 
or occipital chamber of the adult Amia is marked by the trans- 
verse ridge of cartilage that forms the hind wall of the eye- 
muscle canal, and gives support to, and doubtless also origin 
to, the median processes of the petrosals. The antero-ventral 
end of the lateral bounding ridge of the chamber, the hind 
wall of the labyrinth recess, lies opposite the ventral ridge, 
and opposite, or immediately in front of this point, the glosso- 
pharyngeus and vagus have their origins from the brain. The 
glossopharyngeus perforates at once the median, membranous 
wall of the auditory cavity, and transverses that cavity to reach 
its foramen. The vagus, on the contrary, lies always median 
to that membranous wall, running outward and backward along 
it, and then along the posterior surface of the hind wall of the 
labyrinth recess, to its foramen, which lies immediately behind 
the point where the wall or ridge arises from the inner surface 
of the skull. The nerve of the lateral line has a similar course. 
Both nerves, therefore, lie morphologically behind the hind 
wall of the auditory chamber, or, in larvae, behind the hind 
wall of the skull. In the occipital chamber the occipital 
nerves of Sagemehl arise, all of them running outward and 
backward, in the chamber, to their points of exit. 

