VII 



269 



ra 



Fig. III. 



The three chief types o£ Mollusc. A, a Gasteropod (Heto) ; B, a Siphonopod {Sepia) ; C, a 

 Pelecvpod (Anodonta). Al, Anterior adductor muscle ; ^ 2, posterior adductor ; a, anus; e, eye; 

 F foor / fin- g.o, genital opening; *, head; i.g, inner gill; l.p, labial palp; M, mantle-flap ; 

 m, mouth ; 'o.g, outer gill ; p.a, puhnonary aperture ; r.a, retractUe arm : v.h, visceral hump. 



