318 



MARINE INVERTEBRATES 



eo 



Ideal or schematic mollusk. 



1, dorsal view: ft, head; t, cephalic tentacle; sft., shell covering visceral mass; b. m., outline of 

 body-mass; r. m. e., edge of mantle ; c. t., ctenidia, or gills; q. a., generative apertures ; r. e., renal 

 openings ; e. o., excretory opening ; /, posterior portion of foot ; o. e. m., edge of shell. 



2, ventral view : ft. head; t, tentacle; m, mouth; b, outline of body; e.m., edge of mantle; s.f., 

 lower surface of foot ; c. t., ctenidia, or gills ; /, posterior portion of foot. 



3, horizontal section, showing heart, nephridia, and gonads : m, mouth ; o, esophagus ; g, gonad ; 

 p, pericardium ; n, nephridium, or renal organ; v, ventricle ; o, auricles ; g 1 , gonad aperture ; n', 

 renal opening ; e, excretory opening ; /, posterior portion of foot. 



4, vertical median section: m, mouth; b. m., buccal mass; I, liver; d. a., digestive tract; </, 

 gonad ; /, foot ; q. o., gonad aperture, or opening of oviduct ; r. o., renal opening ; e. o., end of diges- 

 tive tract, excretory opening; n, mantle; r, nephridium, or renal orgau ; o./., recurved portion of 

 mantle; *A., shell ; v, ventricle ; p, pericardium. 



