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Prorocentraceae. 



Exuviella Cienk. 



1. E. compressa (Bail.) Ostenfeld, Iagttagelser over Overfladevandets 

 Temperatur, Saltholdighed og Plankton paa islandske og grønlandske Skibs- 

 router, 1899, p. 59 ; Dinopyxis compressa Stein, Der Organismus der In- 

 fusionsthiere III. Abtheil., Leipzig 1878-83, PI. I, f. 34-38. 



6 (rr). 



Area: Almost ubiquitous. 



Prorocentrum Ehrenbg. 



2. P. mica us Ehrenbg. 



1 (rr) - 2 (rr) - 3 (rr) - 6 (rr) - 8 (rr). 



Area: Atlantic, Mediterranean, Red Sea, Indian Ocean. 



Peridiniaceae. 



Pyrophacus Stein. 



3. P. horologium Stein I.e., Pl. XXIV, f. 1-13. 



1 (rr) — 2 (rr) — 7 (rr) — 10 (rr). 



Area: Atlantic, Mediterranean, Red Sea, Indian Ocean, Pacific. 



Ceratium Schranck. 



4. C. tripos (0. F. Müller) Nitsch. 



var. baltica Schutt, Pflanzenleben d. Hochsee, p. 266, f. 4 a. 



I observed two slightly different 

 forms both of which may be referred to 

 the above variety by Schutt. The first 

 form differs from Baltic specimens by 

 the left posterior horn being somewhat 

 bent forward. The second form observed 

 is characterized by the posterior horns 

 being longer and running more parallel. 

 0 I name this form: 



f. parallela Schm. n. f. (see fig. 1). 



It closely approaches to the forms 

 figured by Cleve in Report on the Phyto- 

 Plankton collected on the expedition of 

 H. M. S. „Research", 1896, Fifteenth 

 Annual Report of the Fishery Board for 

 Scotland, Part III, PI. 1, fig. 1, 1897. 



1 (rr) - 2 (rr) - 3 (rr) - 4 (rr) — 6 (rr) 

 8 (rr). . Fig. 1. Ceratium tripos, var. baltica 



Area: Atlantic. Schutt, i. parallela. Ventral view. 



