EXPLANATION OF PLATE XVII. 
FIGURE 86.—Potamilla oculifera, (p. 617 ;) in its tube, with branehie fully expanded, 
from a living specimen, found at Eastport, Maine. 
87.—Cistenides Gouldii, (p. 612 ;) lateral view. 
87a.—The same ; head and branchie, dorsal view. 
88.—Sabellaria vulgaris, (p. 611;) lateral view. 
88a.—The same; view of the operculum and tentacles, from above. 
(Figures 84, 88, 88a were drawn from nature, by J. H. Hmerton; 87, 8ia by A. E. Verrill.) 
