494 ALLIS. [VoL. XII. 
The roof of the eye-muscle canal in the adult is formed, as 
described by Sagemehl, by the horizontal processes of the petro- 
sals, and by a tough, glistening membrane which extends for- 
ward from the front edges of those processes to the transverse 
bar of cartilage. The membrane, however, in all the specimens 
I examined, formed .a much less important part of the roof of 
the canal than in the specimens figured and described by Sage- 
mehl. The processes of the petrosals, the united front edges 
of which have a concave outline, cover nearly, if not quite, one 
half of the canal, and the space between their front edges and. 
the transverse cartilaginous bar is largely occupied by an 
important sack-like depression or pit (pf, Fig. 26, Pl. XXV), 
described by Sagemehl as a slight depression only. In this pit 
are lodged the hypophysis cerebri and saccus vasculosus. The 
rounded front end of the hypophysis projects forward slightly 
beyond the anterior edge of the pit, and almost touches the 
transverse ‘‘Wulst,’” while the saccus vasculosus projects 
backward beyond the hind edge of the opening of the pit and 
lies, in large part, under the projecting, overhanging processes 
of the petrosals in a backward, pocket-like extension of the pit. 
The tough membrane that forms part of the roof of the eye- 
muscle canal extends upward, on each side, and forms the 
median wall of what Sagemehl has called the upper, lateral 
chamber of the canal. In front of the canal the membrane 
extends forward across and beyond the transverse bar of car- 
tilage, closely attached to its upper surface. Here, on each 
side, it extends upward from the lateral edge of the basisphe- 
noid and the cartilage of the basis cranii in front of it, to the 
lower edge of a thin, projecting plate or fin of the alisphenoid, 
and to the lower and posterior edge of the orbitosphenoid in 
front of and continuous with that fin, thus filling the optic 
fenestra. Immediately in front of the transverse bar the mem- 
brane covers and takes part in the formation of a transverse 
pad of tough, dense tissue which extends from orbit to orbit 
(Fig. 26, Pl. X XV), covering and filling the interorbital groove. 
The top of the pad projects backward so as to slightly over- 
hang, and the hind edge thus formed has a concave outline. 
Under this overhanging, curved hind edge, on each side, at the 
