PLATE XVII 



Fig. 242. Polycera Lessonii, 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. 



F-ig. 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. Placobranchus 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. 25G. Herntaea cruciata; from a drawing by Alex. Agassiz of a Naushon 

 specimen. 



