PLATE III. 



Fig. 1. Lyonsiella papyracea, Smith. 



Fi;_;. 1 . The animal seen from tlie ventral aspect, the pallial commissure between the pedal and branchial 



apertures having been cut, and the two lobes of the mantle thrown to the side. 



a, Mouth ; b, c, fold whicli surrouuds the mouth ; d, foot ; e, ventral plate of the gill ; c', dorsal plate 

 of the gill ; h, membrane uniting the gills to the separation of the siphons ; i, free margin of the mantle 

 (pedal aperture) ; j, point where the two lobes of the mantle unite behind the pedal aperture ; k, 

 valvular fold within the branchial aperture ; I, anterior adductor ; q, tentacles of the branchial aperture. 



Fig. 2. Lyonsiella ahyssicola (Sars). 



Fig. 2. The animal seen from the ventral aspect, the two lobes of the mantle having been removed up to 



the line along which tliey are united to the gills. 



a, Buccal aperture ; 6, anterior "palp;" c, posterior "palp;" d, foot; e, ventral plate of the gill; e, dorsal 

 plate of the gill ; h, membrane uniting the gills to the mantle and to the separation of the siphons ; 

 p, anal siphon ; q, tentacles of the iuvaginated branchial siphon. 



Figs. 3-6. Poromya tornata (Jeffreys). 



Fig. 3. The animal viewed from the left side, from which the mantle has been removed, except behind tlie 



line m — q. 



a, Mouth ; h, anterior j.ialp ; c, posterior palp ; (/, foot ; c, branchial partition ; /, visceral mass (liver) ; 

 g, anterior group of lamellaj ; y', posterior group ; h, thick membrane uniting the branchial partition at 

 the separation of the posterior apertures ; »', free margin of the mantle ; j, point where the two lobes of 

 the mantle unite behind the pedal aperture ; };, valve of the branchial aperture ; I, anterior adductor ; 

 m, posterior adductor ; n, posterior retractor of the foot ; o, intestine ; p, heart ; r, tentacles of the 

 liosterior apertures. 



Fig. Jr. The animal seen from the ventral aspect, the mantle having been whoUy removed, as well as the 

 membrane h of the preceding figure. 

 d', Byssal groove ; h, lateral muscle of the branchial partition. The other letters as in fig. 3. 



Fig. 5. The left anterior group of plates. 



a, One plate ; 6, space between two plates ; c, longitudinal bridges. 



Fig. 6. The two posterior apertures. 



a, Branchial aperture ; h, anal apcrt\ire ; «, tentacles. 



Fig. 7. Poromya granulata, Nyst. 



Fig. 7. The animal seen from the left side, from which the mantle has been wholly removed up to the 

 line where it joins the branchial partition. 

 a — n. As in fig. 3 ; /', genital gland ; o, heart ; p, anal siphon ; q, tentacles. 



Figs. 8-10. '' Silenia" sarsi, Smith. 



Fig. 8. The animal seen from tlio left side, from which the mantle has been removed. 



n— /, As in fig. 3 ; <j, anterior group of apertures ; rj, middle group ; </", posterior group. The other letters 

 as in fig. 7. 



Fig. 9. Tlie animal from the ventral aspect, the mantle having been removed from the left side. 

 Letters as in fig. 8. 



Fig. 10. The middle and posterior groups of apertures, much enlarged. 



a, The last two apertures of the anterior group ; h, the middle group ; c, the posterior group ; d, foot. 



