EXPLANATION OF PLATE XXIV. 



FIGURE 137. Littorina nulls, (p. G51 ;) natural si/c>. 



138. Littoriua palliata, (p. 652 ;) natural size. 



139. Lacuna viucta, (p. 052;) enlarged. 



140. Littoriuella miuuta, (p. 653;) enlarged. 



141. Rissoa aculeus, (p. 654 ;) enlarged. 



142. Skenea planorbis, (p. 655;) enlarged. 



143. Odostornia producta, (p. 656;) enlarged. 



144. O. fusca, (p. 656;) enlarged. 



145. O. trifida, (p. 656 ;) enlarged. 



146. O. trifida, var., (p. 656 ;) enlarged. 



147. O. impressa, (p. 656;) enlarged. 



148. O. seminuda, (p. 657;) enlarged. 



149. Euliina oleacea, (p. 655 ;) natural size. 



150. Cerithiopsis terebralis, (p. 648;) enlarged. 



151. C. Emersonii, (p. 648;) enlarged. 



152. Triforis uigrocinctus, (p. 648 ;) enlarged. 



153. Cerithiopsis Greenii, (p. 647;) enlarged. 



154. Bittiura nigruin, (p. 648;) enlarged. 



155. Turbonilla elegaus, ( p. 657 ;) much enlarged. 



156. Margarita obscura, (p. 661 :) natural size. 



157. Yermetus radicula, (p. 649;) natural size. 



158. Caecum pulchellum, (p. (549 ;) natural size and enlarged. 



159. Acm.ra testndiualis, (p. 661 :) natural size. 



159a. The same; lower side, 



1596. The same, variety alveus ; natural size. 



(Figure 155 was drawn from nature, by A. E. Verrill ; the others are from Binney'e Gould, mostly 

 drawn by E. S. Morse.) 



