PLATE 17. 



Figs. 1-7. Strophomenia spinosa, X 33. P'igs. 8, 9, 13. S. ophidiana, X 24. Fig.s. 10-12, 14-17, 

 S. farcimen, X 33. 



Figa. 1, 2, 3 cross sections of S. spinosa (large specimen) along lines A, B, C indicated in fig. 2, 

 pi. 8 (the lines A, B should be perpendicular to the cuticle). 



Fig. 4. Cross section tlirough radula and salivary gland outlet, S. spinosa. 



Figs. 5, 6, 7 are through fig, 4, pi. 9 (posterior end). 



Figs. 8, 9, 13 are cross sections of S. ophidiana along lines A, B, C of fig. 5, pi. 8. 



Figs. 10, 11, 16 are cross sections of S. farcimen along lines. A, B, C indicated in fig. 1, ])1. 7 (ante- 

 rior end). 



Figs. 14, 15, 12, of .same species, correspond to fines D, E, F, of fig. 4, pi. 1 1 (posterior end). 



Fig. 17. Spines of Strophomenia farcimen. X 210. 



