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. 



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



194. — Lyonsia hyalina, (p. 672;) natnral size. 



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



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



197. — Periploma papyracea, (p. 673 ;) natural size. 



198. — Cochlodesma leanum, (p. 673 ;) natural size. 



189.— Petricola pholadiformis, (p. 680 ;) natural size. 



200. — Pholas truucata, (p. 670 ;) natural size. 



(Figure 190 was drawn by A. E. Verrill; all tlie rest are from Biuney's Gould, mostly drawn by E. 

 S. Morse.) 



