726 ALLIS. [Vor. XII. 
between and separates the two sides of the hind end of the 
skull, the cartilage in no place passing either above it or below 
it. Farther forward, where the notochord becomes smaller, the 
sides of the skull recede from it, and a wide cleft is left which 
continues beyond the notochord, and there becomes the hypo- 
physial fenestra of the adult. In later stages the median proc- 
esses of the petrosals develop, approximately at the anterior 
end of the notochord, and the hypophysial fenestra, or anterior 
portion of the cleft, is thus separated from its posterior, occipi- 
tal portion. The ventral portion of the original cleft persists, 
however, in this intermediate portion, as a groove, and is found 
as such even in the adult. The occipital portion of the cleft 
is filled, in the adult, by the median, anterior process of the 
basioccipital. That structure may, therefore, be the ossified 
notochord, if that structure ossifies, or membrane bone, if it 
simply disappears. 
The hypophysial fenestra of the adult Amia seems to be the 
opening, the posterior end of which, in the chick, is said, by 
Froriep (No. 34), to mark the anterior limit of the occipital 
region of the skull. This limit, in the Characinidae, is marked, 
according to Sagemehl, by the anterior end of the basioccipital, 
which extends forward to the hind edge of the petrosal (No. 
106, pp. 42 and 61). In Amia it is marked by the bases of the 
transverse processes of the petrosals. The occipital cleft of 
Amia is, therefore, not found in adult teleosts or in embryos of 
the chick. In the latter the notochord and parachordalia seem, 
from Froriep’s description, to extend as far forward as the 
sphenoid bone, the basisphenoid apparently of Amia. The 
parachordalia in Amia, whatever their anterior limit may be, 
are, posteriorly, a direct continuation of the cartilaginous line 
of the dorsal processes of the vertebrae. 
Antero-ventral to the occipitale laterale in 12 mm. larvae, in 
the triangular space inclosed between it, the base of the skull, 
and the bulging hind end of the auditory capsule, the nervus 
vagus and the two anterior occipital ventral roots have their exit. 
The vagus issues at the upper, anterior angle of the triangle, 
the second occipital nerve near its lower, posterior angle, and 
the first occipital nerve about midway between them. The 

