PLATE XVII 



Fig. 242. Polycera Liessonii, side view ; from a drawing by B. F. Nutting. 



Fig. 243. The same, tentacles. 



Fig. 244. The same, under surface. 



Fig. 245. The same, upper surface. 



Fig. 246. The same, branchial plume. 



Fig. 247. The same, upper surface ; from a drawing by Toppan of a Boston Har- 

 bor specimen. 

 Fig. 248. The same, branchial plume ; from a drawing by Toppan. 



Fig. 249. Placobranclius catulus, — from a drawing by Toppan of an East 

 Boston specimen, — under surface. 



Fig. 250. Same as last, upper surface. 



Fig. 251. Elysia chlorotica ; from a drawing by Dr. Gould. 



Fig. 252. The same, unfolded. 



Fig. 253. The same, outline of head. 



Fig. 254. The same ; from a drawing by Toppan of a Chelsea specimen. 



Fig. 255. Same as last. 



Fig. 256. HermsBa cruciata; from a drawing by Alex. Agassiz of a Naushon 

 specimen. 



