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