MYODOME AND TRIGEMINO-FACIALIS CHAMBER Pay A 
basisphenoid would seem to show that, as already stated, the 
anterior portion of the basisphenoid of Hyodon did not pri- 
marily form part of this bone. 
‘The cross-commissure connecting the efferent pseudobran- 
chial arteries of opposite sides traverses the ventral part of the 
‘prespinal portion of the myodome, there passing ventral to the 
orbito-nasal artery and anteroventral to the internal carotids. 
The pituitary veins enter the dorsal compartment of the my- 
odome and there anastomose with each other, a small branch 
being sent upward into the cavum cerebrale cranii and appar- 
ently going to the hypophysis. 
The nervus palatinus facialis of the adult traverses a canal 
in the prootic which begins in the floor of the pars jugularis of 
the trigemino-facialis chamber and opens on the mesial surface 
of the ventral process of that bone in the plane of the hind edge 
of the pituitary opening of the brain case, the nerve thus ap- 
parently not traversing the dorsal compartment of the myo- 
dome. In the 65-mm. specimen the nerve does not enter the 
pars jugularis of the trigemino-facialis chamber, perforating the 
roof of the dorsal compartment of the myodome and traversing 
it, as in Hyodon, but, as also in Hyodon, there lying between 
the ventral process of the prootic and the lining membrane of 
the myodomic cavity. 
MAIL-CHEEKED FISHES (LORICATI) 
In the adults of Scorpaena scrofa, Trigla hirundo, and Cot- 
tus octodecimospinosus, I found (Allis, 709) the myodome to 
extend nearly to the hind end of the basioccipital, and there 
open ventrally. In Scorpaena the origins of all the rectus 
muscles were given, the external and internal ones extending 
posteriorly in the myodome, the external somewhat farther than 
the internal. Nothing was said of a horizontal membrane sep- 
arating the myodome into dorsal and ventral compartments, 
such as I had previously described in Scomber and now find 
in Hyedon. The orbital opening of the myodome was said 
to be closed by a strong membrane which the recti externi and 
interni perforated to reach their points of origin. 
