EXPLANATION OF PLATE XXIV. 
Figure 137.—Littorina rudis, (p. 651;) natural size. 
138.—Littorina palliata, (p. 652 ;) natural size. 
139.—Lacuna vincta, (p. 652;) enlarged. 
140.—Littorinella minuta, (p. 653 ;) enlarged. 
141.—Rissoa aculeus, (p. 654;) enlarged. 
142.—Skenea planorbis, (p. 655;) enlarged. 
143.—Odostomia producta, (p. 656 ;) enlarged. 
144,—O. fusca, (p. 656 ;) enlarged. 
145.—O. trifida, (p. 656 ;) enlarged. 
146.—0. trifida, var., (p. 656 ;) enlarged. 
147.—O. impressa, (p. 656;) enlarged. 
148.—O. seminuda, (p. 657 ;) enlarged. 
149.—Eulima oleacea, (p. 655 ;) natural size. 
150.—Cerithiopsis terebralis, (p. 648 ;) enlarged. 
151.—C. Emersonii, (p. 648;) enlarged. 
152.—Triforis nigrocinctus, (p. 648 ;) enlarged. 
153.—Cerithiopsis Greenii, (p. 647;) enlarged. 
154.—Bittium nigrum, (p. 648;) enlarged. 
155.—Turbonilla elegans, (p. 657;) much enlarged. 
156.—Margarita obscura, (p. 661;) natural size. 
157.—Vermetus radicula, (p. 649;) natural size. 
158.—Cecum pulchellum, (p. 649 ;) natural size and enlarged. 
159.—Acmeea testudinalis, (p. 661 ;) natural size. 
159a.—The same; lower side, 
159b.—The same, variety alveus; natural size. 
(Figure 155 was drawn from nature, by A. E. Verrill; the others are from Binney's Gould, mostly 
drawn by E, 8. Morse.) 
