EXPLANATION OF PLATE XXI. 
Ficvure 106.—Pleurotoma bicarinatum, (p. 638;) natural size. 
107.—Bela plicata, (p. 637 ;) natural size. 
108.—Bela harpularia, (p. 636;) natural size. 
109.—Anachis similis, (p. 644 ;) natural size. 
110.—Astyris lunata, (p. 645 ;) enlarged. 
111.—Astyris zonalis, (p. 645 ;) enlarged. 
112.—Tritia trivittata, (p.641;) natural size. 
113.—Ilyanassa obsoleta, (p. 641 ;) natural size. 
114.—Nassa vibex, (p. 640;) natural size. 
115.—Neptunea pygmza, (p. 639 ;) natural size. 
116.—Urosalpinx cinerea, (p. 641;) natural size. 
117.Eupleura candata, (p. 642;) natural size. 
118.—Purpura lapillus, (p. 642;) natural size. 
119.—The same; banded variety. 
120.—The same; egg-capsules, enlarged one-third. 
121.—Buecinum undatun, (p. 638 ;) natural size. 
122.—Scalaria multistriata, (p. 660 ;) enlarged. 
123.—Scalaria lineata, (p. 660;) enlarged. 
(Figure 120 was drawn from nature by J. H. Emerton; the rest are from Binney's Gould, drawn by 
E. S. Morse.) 
