PLATE XVIII. 



Figs. 1-5. Sti/ela squamosa, Herdman. 

 Figs. 1 and 6-8. Styela bythia, Herdman. 



Fig. 1. A black manganese nodule, to which are attached a Brachiopod and two species 



of Styela. The upper specimen is Styela squamosa, the lower is Styela bythia ; 



natural size. (From a drawing by Mr. George West.) 

 Fig. 2. Part of the branchial sac of Styela squamosa, seen from the inside ; magnified 



(Hartn., obj. 4). 

 Fig. 3. Part of the circle of tentacles of Styela squamosa, showing two sizes (in. and tn.') ; 



magnified (Hartn., obj. 4). 

 Fig. 4. Small portion of the branchial sac of Styela squamosa, showing a fold (br.f.), 



seen from the inside ; magnified (Hartn., obj. 4). 

 Fig. 5. Another part of the branchial sac of Styela squamosa, seen from the inside, show- 

 ing a piece of the dorsal lamina (d.l.) ; magnified (Hartn., obj. 4). 

 Fig. 6. Part of the branchial sac of Styela bythia, seen from the inside, showing the 



closely- placed and crumpled internal longitudinal bars (i.l.) ; magnified 



(Hartn., obj. 4). 

 Fig. 7. A small portion of the last figure, much magnified, to show the wavy outline of 



the stigmata (Hartn., obj. 5). 

 Fig. 8. Part of the dorsal lamina of Styela bythia, showing the languets (/.); magnified 



(Hartn., obj. 4). 



