PLATE I. 



Fio-s. 1, 2. Guivillea alahastrina, Watson. 



Fig. 1. Anterior portion seen from the right side. 



a, Proboscis ; 6, cephalic veil ; c, left tentacle ; d, rudimentary right eye ; e, foot ; /, penis ; g, mantle ; 

 h, pallial siphon ; i, entrance to the pallial chamber ; j, appendage of the siphon. 



Fig. 2. Sagittal section of the rudimentary eye. 



a, Epithelium ; /), pellucida ; c, subcutaneous connective tissue ; d, common sheath of tlie optic nerve and of 

 the ball of the eye (clioroid) ; e, homogeneous retinal mass ; /, beginning of the optic nerve ; g, mus- 

 cular mass of the cephalic veil. 



Figs. 3-5. Trochus infundibulum, Watson. 



Fig. 3. Anterior portion and foot, seen from the ventral side and slightly to the left. 



a, Buccal .aperture ; h, right labial palp ; c, left tentacle, with the eye at its base ; d, mantle ; e, pallial 

 cavity ; /, anus ; <7, foot ; h, anterior epipodial lobe ; i, epipodial tentacles. 



Fig. 4. Head from the dorsal aspect. 



a, Buccal aperture ; h, labial palp ; c, tentacle; d, eye; e, "palmette." 



Fig. 5. Anterior portion of the nervous system, seen from the right side. 



a, a', C'erebr.il ganglia ; h, cerebral commissure ; c, cerebro-pleural connective ; d, cerebro-pedal connective ; 

 e, "labial prominence" of the cerebral ganglion;/, proboscideal nerves; g, tentacular nerve; 

 h, nerve of the labial palp; i, nerves of the lips; j, origin of the sub-oesophageal "labial com- 

 missure." 



Fig. 6. Dolahella neapolitana, Delle Chiaje. 



Fig. 6. Anterior portion and foot, seen from the ventral side, and slightly to the left. 



a, Buccal aperture ; h, labial palp ; c, anterior tentacle ; d, posterior tentacle, with the eye at its base ; 

 e, foot. 



Figs. 7, 8. Malletia pallida, Smith. 



Fig. 7. The animal is viewed from the left side, and the pallial lohe of that side has been remo^•ed, ivith the 

 exception of the retractor muscle of the siphons. 



a, Buccal aperture ; h, left labial palps ; c, their appendage contracted ; d, foot ; e, visceral mass ; /, right 

 lobe of the mantle ; g, left gill ; h, branchial siijhon ; i, anal siphon ; j, siphonal tentacle ; k, left 

 retractor muscle of the siphons ; I, anterior sdductor muscle ; m, posterior adductor muscle ; n, posterior 

 retractor muscle of the foot. 



Fig. 8. Left giU, seen from the outer side. 



a. Branchial axis ; b, outer row of lamella; ; c, inner row of lamellie. 



Fig. 9. Macoma halthica (L.) {TcUina). 



Fig. 9. Posterior portion, seen from the left side, with the mantle removed from that side to the line x — .r'. 



d, Foot ; /, right lobe of the mantle ; g, left gill ; Ji, branchial siphon ; i, anal siphon ; j, siphonal ten- 

 tacular tuft ; right retractor muscle of the siphons ; I, posterior adductor muscle ; ?n, posterior retractor 

 muscle of the foot ; o, muscle of the pallial commissure. 



