624 



In the Færoes I found it in Sorvaagsvatn (Vaago); the large 

 lake near Ejde (Ostero); Sandsvatn (San do); and the lake in Kvan- 

 hauge (Sydero). 



16. P. umbonatum Stein, Organistnus der Infusionsthierchen, 

 III. Abteil., 2 Håll'te, 1883, PI. XII, ligs. 1—8; A. I. Schilling, 1. c., 

 p. 73, PI. III, fig. 15. 



In one of the samples from Sorvaagsvatn, occurred, as well as 

 the ahove-mentioned species, a single individual of a smaller spe- 

 cies which, as regards its appearance, and the distribution of its 

 plales agrees with the figures of P. umbonaliun given by Stein and 

 Schilling, with the exception that the dorsal apical piates differed 

 slightly from those seen in Schilling's diagram. 



17. Ceratium hirundinella (O. F. Mull.) Schrank. 



This widely distributed plankton-form, the only freshwater Peri- 

 diniacea which is important owing to its quantity, appears to be 

 strangely rare in the Færoes; at any rate during those seasons 

 when the samples which have been examined were gathered il was 

 almost absent. I found a few dead individuals in the lake in Kvan- 

 hauge, and in the large Sorvaagsvatn only a few individuals occur- 

 red. The individuals observed belong to the 3-horned temporal variely. 



