20 
transmits the origins of the two right oblique muscles of 
the eye. The ethmoid cartilage appears on the surface of 
the skull on each side of the mesethmoid immediately 
above the vomer. It is bounded by the parasphenoid, the 
prefrontals, mesethmoid and vomer. 
Vomer (Vo., figs. 1, 2, 35)—A median unpaired bone 
consisting of an anterior head and a posterior shaft taper- 
ing to a point. The latter is firmly fixed into a long 
tapering cavity in the base of the parasphenoid to such an 
extent that the extremity of the parasphenoid is brought 
very near the anterior end of the vomer. The cavity in 
the parasphenoid lodging the vomer is quite distinct from 
that immediately above it for the ethmoid cartilage and 
the left prefrontal. The head of the vomer is inarkedly 
asymmetrical, and has a laminate process on each side, the 
right of which is appreciably larger than the teft. In 
front the vertical face is inclined towards the eyeless side, 
thus further deflecting the motion of the intermaxillary 
cartilage, and hence the jaw apparatus, to that side. The 
vomer is bounded by the parasphenoid, prefrontals, 
ethmoid cartilage and mesethmoid. 
Parasphenoid (Pa.S., figs. 1, 2, 5)—A very Jong un- 
paired bone with a prominent keel. It is very asymmetri- 
eal, taking at the region of the alisphenoids a sharp turn 
towards the eyeless side. Behind it fits into a depression 
on the base of the basioccipital, and forms a portion of the 
floor of the cranial cavity in front of the latter bone, its 
dorsal surface being here deeply grooved. Its relations 
in front to the ethmoid cartilage, left prefrontal and 
vomer have been described above. The parasphenoid is 
bounded by the basioccipital, prootics, alisphenoids, left 
prefrontal, ethmoid cartilage and vomer. 
Nasal (/?.WVa., figs. 1, 2, 3)—Only the right nasal is 
present—the left having completely aborted with the 
