264 EDWARD PHELPS ALLIS, JR. 
sphenoid instead of passing internal to the ascending process 
of that bone. Whether or not there is a subpituitary portion 
of the dorsal myodomic cavity I cannot determine, the mem- 
branes being in a more or less disintegrated condition. It is, 
however, apparently wanting, for there are no veins compar- 
ble to the pitutary veins of the other Teleostei considered, the 
pituitary region being drained by veins definitely in the cavum 
cerebrale cranii. Furthermore, the membranous pituitary sac 
apparently forms the perichondrial lining of the pituitary fossa, 
as it also does of the larger part of that fossa in the Selachii. 
There is no pars jugularis of a trigemino-facialis chamber. 
The internal carotid artery gives off, as described earlier 
(Allis, ’08 b), an orbitonasal artery, sends two branches to 
the eyeball, and then enters the cranial cavity through the fo- 
ramen opticum, behind the nervus opticus. This latter nerve 
certainly lies dorsal to the trabecula. The internal carotid 
artery of this fish must then also have that relation to that car- 
tilage, the artery accordingly entering the cranial cavity by 
passing, first lateral and then dorsal to the trabecula. 
AMIA CALVA 
In Amia (Allis, 97, etc.) the myodome lodges the external 
rectus muscles and the pituitary veins, and corresponds to 
the dorsal compartment only of the myodome of Teleosts. 
It has no basioccipital extension, being limited to the subpitui- 
tary and prootic regions. The: hypophysis and saccus vascu- 
losus, both enclosed in the membranous pituitary sac, project 
ventrally into this myodomie cavity, the hypophysis lying im- 
mediately posterior to the presphenoid bolster and the saccus 
projecting posteriorly beneath the prootic bridge. The other 
rectus muscles have their origins on the lateral surface of the 
presphenoid bolster. The myodome has a large orbital open- 
ing, bounded laterally by the pedicel of the alisphenoid, and 
the nervus profundus and vena jugularis traverse this opening 
to enter the trigemino-facialis chamber, the recti externi tra- 
versing it to enter the myodome, and the oculomotor and troch- 
learis nerves traversing it to reach their primary foramina, 
