MYODOME AND TRIGEMINO-FACIALIS CHAMBER 265 
which lie in the membranous wall of the cavum cerebrale cranii. 
All of these structures thus pass mesial to the pedicel of the 
alisphenoid, as do also, morphologically, the pituitary vein 
and the abducens nerve. The arteria carotis externa and the 
nervi maxillaris and mandibularis trigemini, on the contrary, 
pass lateral to this pedicel to enter the trigemino-facialis chamber. 
The trigemino-facialis chamber is not separated by a wall 
of bone into ganglionaris and jugularis parts, as in most of 
the Teleostei, and, because of the absence of a bony floor, the 
chamber is in direct communication with the myodomic cavity. 
A ventral compartment of the myodome, as a functional myo- 
domie cavity, is wholly wanting in this fish, but is represented 
in certain canals traversed by the internal carotid and efferent 
pseudobranchial arteries, the internal carotid artery of either 
side being accompanied, in part of its course through its canal, 
by the palatine branch of the facialis and the pharyngeal branch 
of the glossopharyngeus. These several canals were fully 
described in an earlier work (Allis, 97, p. 496) and were there 
called the palatine, internal carotid, and efferent pseudo- 
branchial canals. The palatine canal of either side, as there 
described, les between the parasphenoid and the ventrolateral 
surface of the chondrocranium, and the nervus palatinus facialis 
enters it at a certain distance anterior to its‘ hind end, the pos- 
terior portion of the canal lodging only the internal carotid 
artery and the pharyngeal branch of the nervus glossopharyn- 
geus The internal carotid canal arises from this palatine canal 
and, running upward, traverses the cartilaginous presphenoid 
bolster to enter the cavum cerebrale cranii. The efferent pseu- 
dobranchial canal is in two sections, one of which traverses the 
lateral bounding wall of the. orbital opening of the myodome, 
while the other penetrates the presphenoid bolster to fall into 
the internal carotid canal. My palatine canal is the canalis 
parabasalis of Gaupp’s (’05 a) account of Lacerta, and conditions 
in other vertebrates, to be later considered, show that it should 
be considered as formed by the fusion of two canals, one tra- 
versed by the nervus palatinus facialis and the other by the 
nternal carotid artery. 
