244 EDWARD PHELPS ALLIS, JR. 
prootic, but they are not shown in the figure. It is however 
probable that the conditions resemble those in Hyodon, the 
myodome evidently being large and having a large orbital open- 
ing on either side. Whether or not there are both dorsal and 
ventral compartments to the myodome cannot be told, but 
they are probably both present. Supino says that a basi- 
sphenoid is found, which must accordingly separate the so-called 
pituitary fossa of Handrick’s descriptions into a pituitary open- 
ing of the brain case and a foramen formed by the fusion of the 
foramina optici, and he adds that: ‘‘ Posteriormente l’estremita 
delle porzione impari del basisfenoide si congiunge, nel Chau- 
loides e Argyropelacus, con la cartilagine che si trova nella 
cavitaé dei muscoli oculari.”’ This, while not quite clear, would 
seem to mean that cartilage formed some part of the floor of 
the myodome. 
ESOX 
In the adult Esox the myodome is large and extends pos- - 
teriorly into a conical excavation in the anterior end of the basi- 
occipital, as Huxley (71) has stated. A horizontal membrane 
separates it into dorsal and ventral compartments, the dorsal 
one being large and lodging the recti externi, while the ventral 
one is short, extending, posteriorly only to the hind edges of the 
foramina for the internal carotid arteries. From there the 
membrane separating the two compartments rises rapidly to 
the ventral surface of the relatively deep membranous pitui- 
tary sae, fuses with that surface, and then appears as two sep- 
arate membranes, each having its mesial attachment on the 
ventrolateral surface of the sac. The recti interni have their 
origins beneath this membrane, on the floor of the ventral com- 
partment of the myodome, near its hind end. The recti sup- 
periores have their origins from the anterior edge of each half 
of the horizontal membrane, near its dorsomesial end, and the 
recti inferiores from the lateral walls of the spreading dorsal 
end of the median vertical membrane, immediately an- 
terior to the membranous pituitary sac. This median vertical 
membrane is party fused with the median portion of the hori- 
