50 P. T. CLEVE. PLANKTON, COLLECTEI) B\ THE SWEDISII EXPEDITION TO SPITZBERGEN. 



Plate III. 



Pag. 



Fig. 1. Peridium (?) minutum Cl. Ii and c The same shell in different foci 31. 



■> 2. Pliorticium pyloninm Hkl. a, h, c The shell in different state of development, d The primordial 



shell 31. 



» 3. Plectanium (?) simplex Cl 32. 



» 4. Polj'petta bolostoma Cl. a The shell, h Structure 32. 



» 5. Theocorvs borealis Cl 33. 



