MYODOME AND TRIGEMINO-FACIALIS CHAMBER 223 
membrane which forms the anterior wall of the membranous 
pituitary sac. In this part of its course, and while still enclosed 
in the median vertical membrane, it anastomoses with its fel- 
low of the opposite side, and then, separating from its fellow, 
enters the cavum cerebrale cranii (fig. 2). There it immedi- 
ately divides into anterior and posterior divisions. The pos- 
terior division sends branches to the hypophysis, and then itself 
separates into anterior and posterior branches. The anterior 
branch runs forward along the floor of the cavum cerebrale 
eranii and sends a branch outward in the body of the optic 
nerve. Other branches are sent to the brain, one of them join- 
ing, anterior to the nervus opticus, the terminal portion of the 
anterior division of the entire artery. In one of two specimens 
examined, the latter division of the artery immediately issued 
from the cranial cavity by passing ventrally across the posterior 
edge of the basisphenoid, while in the other specimen it perfor- 
ated that bone near its hind edge. In each case the artery then 
ran forward ventral to the horizontal plate of the basisphenoid, 
enclosed in the dense fibrous tissues that there form the dorsal 
edge of the interorbital septum. While in this tissue a branch 
is sent outward to the eyeball, the artery then issuing from the 
fibrous tissue, passing across the posterodorsal surface of the 
nervus opticus, and entering the cranial cavity through the fora- 
men for that nerve. There it joins and fuses with the anterior 
branch of the posterior division of the entire artery, just de- 
cribed, the artery so formed then running forward along the 
floor of the cavum cerebrale cranii. The branch sent to the 
eyeball from the anterior division of the artery, enters it close 
to the point of entrance of the nervus opticus, and there im- : 
mediately forms a slight enlargement which somewhat resembles 
a glomus. From this glomus a branch arises and unites with 
the small artery accompanying the nervus opticus, the two to- 
gether forming the arteria centralis retinae. 
I cannot recognize the anterior division of the internal ca- 
rotid artery, above described, in any descriptions that I have of 
the adults of fishes, and yet it is found in all of the non-siluroid 
Teleostei that I have examined in serial sections in connection 
