158 KAARE MÜNSTER STRØM. 



Genus Gymnodinium. Stein 1883. '■ 



28. Gymnodinium fuscum. (Ehrbg.) Stein : Organismus. 

 Somewhat rare. In two samples. 



Family Peridiniaceæ. 

 Genus Glenodinium. Stein 1883. 



29. Glenodinium uliginosum. Schill. Süsswasserperidin. 

 Common, but never in great abundance. I find the size of 



this common form to be very variabel, the length of the speci- 

 mens exammed by me varying from 25 to 38 ,«. All the forms 

 were quite typical, and all intermediate stages were met with, 

 so that is no reason to make a seperate form or even a variety 

 of the smaller specimens observed. 



30. Glenodinium cinctum. Ehrbg. Infus. 

 Rare. Onlv a few specimens observed. 



Genus Peridinium. Ehrbg. 1830. 



31. Peridinium cinctum. Ehrbg. Infus. 



General, but never in great abundance. Fig. 10, Pi. V. 



32. Peridinium Willei. Huitf.-Kaas. Limn. Peridin. 

 In one or two samples. 



33. Peridinium inconspicuum. Lemmermann: Abb. Nat. 

 Ver. Brem. XVI. 



Not uncommon, but scarce. 



34. Peridinium tabulatum. (Ehrbg.) Clap. & Lachm. 

 Etudes. Infus. 



Only in a single sample, but in some quantity. 



Genus Ceratium. Schrank 1793. 



35. Ceratium hirundinella. (0. F. M.) Schrank: Briefe 

 nat. phys. 



Only a single specimen in the plankton. It is quite possible 

 that this species may be very frequent in the plankton of 

 other months. 



