588 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
the second (fig. 76, 6 and c). The fourth pair run 
forwards and outwards over the wall of the sinus. Thus 
they cross over the buccal nerves which run forwards and 
inwards (fig. 76, d, and B. V.). Hach of the two gives off 
two branches, an inner and an outer. The three branches 
thus obtained now run over the wall of the sinus to end 
in the lip. 
A. (4) Buccal Nerves.—These are two nerves much 
stouter than the labial. Running from the outer anterior 
angle of the cerebral ganglion each nerve pierces the 
anterior cranial wall, and then runs inwards towards the 
sub-oesophageal ganglion (Pl. VIII, fig. 72, B.W.). 
Arriving at the posterior lateral wall of the buccal mass, 
this nerve divides into three branches (fig. 72, D., JZ. and 
V.). Of these, the most dorsal runs up to the sub- 
oesophageal ganglion, the median ends in branches in 
the buccal wall, while the ventral one curves downwards, 
and ends similarly in the wall of the buccal mass. The 
innermost branch given off from this ventral nerve runs 
towards its fellow from the other side and meets 1 
just below the initial part of the radula sac, swelling 
here to form a small, oval sub-radular ganglion (fig. 72, 
ToD.) 
Ophthalmic Nerves.—'l’o see these it is best to 
expose the eyes from the dorsal surface by dissecting 
away the skin and superficial muscles from the back of 
the head (Pl. IX, fig. 74, #.). Thus the muscles which 
dorsally cover the brain case and the bases of the arms 
are also exposed (fig. 74, 6, and a). There are three 
eroups of ophthalmic nerves on each side:—(1) three 
anterior superior, (2) cne posterior superior, and (3) three 
inferior. 
A. (5) The Anterior Superior Ophthalmic are three 
fine nerves, which arise dorsal to the origin of the optic — 
| =. x SP , 
