1892.] The Head of an Embryo Amphiuma. ` 673 
either side it merges with the posterior angle of the otic cap- 
sules; above it is incomplete. Between the ventral portion of 
the occipital vertebre and its lateral union with the otic cap- 
sule is the foramen for the vagus nerve. 
The otic capsules are elongate oval. In front they project 
slightly beyond the point of union with the criste trabecula- 
rum, behind they merge into the occipital vertebra. In the 
lower outer surface is the large oval foramen ovale, and just 
in front of it is the external opening of the foramen for the 
facialis. This foramen does not penetrate the ear capsule 
proper, it only passes through its anterior wall. On the inner 
lower surface the otic capsule is produced into a narrow ledge 
which projects inwards to form a part of the floor of the cranial 
cavity, being limited internally by the large opening between 
itand the parachordal cartilage. The inner wall of the capsule 
is perforated by three subequal openings in the same plane, 
and a fourth smaller one above them and between the two 
posterior ones. The anterior of these forms a considerable 
cavity, in which is situated the acustico-facialis ganglion and 
from it nerves go through the adjacent cartilage in the follow- 
ing directions: One branch, the ramus palatinus, goes ven- 
trally through the floor; a second, the facialis proper, goes 
straight outward to reappear, as just mentioned, upon the 
outer surface; while the third, the ramus vestibularis of the 
eighth nerve, goes upward and backward to the sensory epi- 
thelium of the inner ear. Separated by a considerable carti- 
laginous interval from the first of these openings is a second, 
nearly equal in size, through which the ramus cochlearis of 
the auditory nerve enters the ear; the small upper opening 
permits the ductus endolymphatieus to pass above the brain 
in the same manner that the ductus perilymphaticus goes 
through the fourth opening beneath the brain. I have seen 
no special opening in the cartilage for the passage . blood- 
vessels to the inner ear. 
CARTILAGINOUS VISCERAL SKELETON.—The tiiis is 
rhomboidal in outline when viewed from the side, the external 
surface exhibiting a slight depression. As yet it is connected 
with the skull by only the process ascendens, the processes 
