MYODOME AND TRIGEMINO-FACIALIS CHAMBER 257 
referred to; a middle section, ‘‘der in der Fissur der Schiidel- 
basis, bezw. in einem nach unten offenen Sulcus liegt,’ and a 
posterior section which les wholly beneath the basis eranii. 
Reference is here made by Schleip to a series of half schematic 
figures (l. c., pp. 355 to 357), and consideration of them shows 
that the so-called anterior section of the myodome is what I 
have called, in the fishes described by me, its prespinal section. 
The middle section is apparently my prootic portion of the spinal 
section, and the posterior section what I have called the basioccip- 
ital portion of that section. A membrane is shown in these 
figures extending transversely between the ventral ends of the 
ventral processes of the prootic cartilages and separating the 
recti externi from the recti interni. This membrane is the hori- 
zontal myodomic membrane of my descriptions, but I cannot 
find that Schleip refers to it in his text, for the transverse mem- 
brane of his descriptions is said to form the roof of the myodome. 
In a 25-mm. embryo of Salmo salar Gaupp finds conditions 
strikingly similar to those described by Swinnerton in Gaster- 
osteus, and he arrives at practically similar conclusions regard- 
ing the development of the myodome, without, however, here 
making special reference either to that author’s or to Schleip’s 
conclusions regarding it. Like Schleip, Gaupp (05 b, pp. 665 
to 669) separates the myodome into anterior, middle, and pos- 
terior sections. ‘The anterior section is said to lie in the poste- 
rior portion of the orbitotemporal region, and its floor to be 
formed by the two trabeculae and a membrane which extends 
transversely between them. ‘The space between the two tra- 
beculae is called by Gaupp the fenestra basicranialis anterior, 
or fenestra hypophyseos, and it corresponds to the intertra- 
becular, or pituitary fossa of Swinnerton’s descriptions of Gas- 
terosteus. It, however, apparently corresponds to the anterior 
portion only of the intertrabecular, or pituitary fossa of Schleip’s 
description of the trout, the hind ends of the trabeculae of 
Schleip’s account corresponding to the anterior prolongations of 
the parachordals of Swinnerton and Gaupp. The membrane 
said by Gaupp to close the fenestra hypophyseos of Salmo is 
shown by him, in a figure of a cross-section through this region 
