EXPLANATION OF THE PLATES. 



;i anus. 



aor aorta. 



ap antcnur [icdal g,laiul. 



b brain. 



be buccal comrni.s.-surc. 



bg labio-buc'cal ganglion. 



br gill. 



brn nerves to gills. 



c intestinal coecnni. 



(■] cloaoal chaml)er. 



en cloacal eoccum. 



cp coelomoduct . 



da dorsal aorta. 



dsg dorsal salivary gland. 



fo b\iccal |)latr. 



gl glands nf |i|iarynx, 



gon gonad. 



lit heart. 



int intestine. 



Ibj labio-bueeal connective 



liv liver. 



in mouth. 



n nerve to buccal plate. 



DC oesophagus. 



\>r p.'dal ganglion. 



peg |ircc<'rcl)r;d .nanghou 



prill pcrii-anliuin. 



pli pharyn.x. 



pi l.ileral ganglion. 



ps pi'dal sinus. 



r radula. 



r;> seminal recejitacle. 



rs radular su|>iiorl. 



s anterior vertii'al scpruin 



sc subradular coniniissure. 



sg ventral salivary gland 



sgl shell gland. 



sn svibradular ganglion. 



so sense organ. 



sp spii'ule, 



sr iliHs.il gill rcl ractcir. 



sro siilir.iclular organ. 



sto stoiiKicli. 



sv seminal vesicle. 



vr ventral gill retraiior, 



vs ventral diaiiliragm. 



