EXPLANATION OF THE PLATES. 



oe oesophagus. 



pc pedal ganglion. 



peg precerebral ganglion. 



pcm pericardium. 



ph pharynx. 



pi lateral ganglion. 



ps pedal sinus. 



r radula. 



re seminal receptacle. 



rs radular support. 



s anterior vertical septum 



sc subradular commissure. 



sg ventral salivary gland 



sgl shell gland. 



sn subradular ganglion. 



so sense organ. 



sp spicule. 



sr dorsal gill retractor. 



sro subradular organ. 



sto stomach. 



sv seminal vesicle. 



vr ventral gill retractor. 



vs ventral diaphragm. 



