EXPLANATION OF PLATE XXVII. 



FIGURE 186. Teredo navalis, (p. 669;) shell and pallets. 



187. Teredo Thomsoni, (p. 670;) shell and pallets. 



188. Teredo megotara, (p. 670;) shell and pallets. 



189. Xylotrya fimbriata, (p. 670;) shell and pallets. 



190. Gastranella tumida, (p. 678;) shell, enlarged six diameters. 



191. Corbula contracta, (p. 672;) natural size. 



192. Saxicava arctica, (p. 671 ;) natural size. 



193. Clidiophora trilineata, (p. 673;) natural size, with animal. 



194. Lyonsia hyalina, (p. 672;) natural size. 



195. Thracia truncata, (p. 674 ;) natural size. 



196. Thracia myopsis, (p. 673;) natural size. 



197. Peri ploma papyracea, (p. 673;) natural size. 



198. Cochlodesma Leanum, (p. 673 ;) natural size. 



199. Petricola pholadiformis, (p. 680 ;) natural size. 



200. Pholas truncata, (p. 670 j) natural size. 



(Figure 190 was drawn by A. E. YerriU : all the rest are from Binney s Gould, mostly drawn by E. 

 S. Morse.) 



