14 
by the basi-occipital and opisthotic, and internally by its 
fellow of the opposite side. It bears a conspicuous 
foramen with a long canal (f.vg., figs. 2, 3) for the exit of 
the vagus nerve, and at least one other for the first spinal 
nerve. 
Supraoccipital (S.O., figs. 1, 4)—A large asymmetri- 
cal bone hardly appearing on the occiput, from which it is 
excluded by the epiotics, and having only a feeble 
occipital spine (Oc.S.), so well marked in the Cod. This 
spine and ridge is continued forwards to the left anterior 
corner of the bone, where it forms a furrow developed in 
connection with the interspinous bones or axonosts of that 
part of the dorsal fin situated over the head, as elsewhere 
described. In front the supraoccipital is thin and 
laminate, so that the roof of the cranial cavity is here very 
slender, but behind the cerebral surface cf the bone is 
supported by three strong ridges of bone and cartilage. 
The supraoccipital is bounded in front by the frontals, 
laterally by the parietals, and behind by the epiotics. 
The basi-, ex- and supraoccipitals together form the 
occipital segment of the cranium. 
The Auditory Capsule of the Plaice is formed by the 
following five bones, as in the Cod: — 
Sphenotic (Sp.0., figs. 1, 2, 3)—Does not contain 
much cartilage. Externally on the dorsal surface a strong 
process is sent out and supported by a ridge of bone 
coming up from below. The sphenotic forms the external 
and upper half of the deep cup for the ball of the 
hyomandibular (cp. fig. 5), the prootic half of the same 
being more or less separated from it by a strip of the 
chondrocranium (cp. the two sides in fig. 2, Hm.F.*). 
The cerebral surface of the sphenotic has two large cavities 
separated by a thick wall of bone and cartilage. The 
sphenotics are not quite symmetrical—that of the ocular 
: 
