274 EDWARD PHELPS ALLIS, JR. 
pituitary fossa perforated by a cord of tissue. It is not said 
what this cord of tissue is, but it is undoubtedly the pituitary 
vein described by me (Allis, 08a) in a 75-mm. specimen of Polyp- 
terus senegalus. This pituitary vein falls into a vein that I 
called the internal jugular, but which is more appropriately called 
the vena orbitalis inferior. This vein comes from the orbit, ac- 
companied by the internal carotid artery and the nervus palati- 
nus facialis, and after receiving the pituitary vein, is joined 
by a vein that I called the external jugular, but which is a vena 
orbitalis superior and is accompanied by the external carotid 
artery. The yein formed by the fusion of these two is the vena 
jugularis of the present descriptions. Running posteriorly, 
it traverses a short canal in the cartilaginous portion of the 
lateral wall of the chondrocranium, between the foramina by 
which the nervi trigeminus and facialis traverse that wall, and 
issues from the cranium, with the nervus facialis, at the hind 
edge of the ascending process of the parasphenoid. The ex- 
ternal carotid artery unites with the internal carotid, and the 
artery so formed continues posteriorly in a canal through the 
ascending process of the parasphenoid, accompanied by a sym- 
pathetic nerve. At the hind end of this canal it receives the 
efferent artery of the hyoid arch, and then, becoming the lateral 
dorsal aorta, enters the aortal canal in the basioccipital, already 
referred to when describing the conditions in Hyodon. 
The conditions in this fish are thus markedly different from, 
but nevertheless strictly homologous to, those in the other fishes 
so far considered. ‘There is a dorsal myodomic cavity strictly 
similar to that in the Holostei, and a ventral compartment rep- 
resented by the canals through the ascending processes of the 
parasphenoid. The median portion of the parasphenoid and 
the lateral walls of the canals through the ascending processes 
of that bone must then, together, correspond to the parasphenoid 
of Amia, the mesial walls of the latter canals corresponding to 
the ascending processes of the parasphenoid of Amiurus. The 
canal traversed by the vena jugularis, which lies partly in the 
lateral wall of the chondrocranium and partly between that 
wall and the lateral wall of the ascending process of the para- 
sphenoid, is the pars jugularis of a trigemino-facialis chamber. 
