578 



thcse organisms, see Jorgensen in »Bergens Museums Aarbog«, 

 1899, No. VI, pp. 47—49, Ostenfeld, Iagttagelser, etc, 1900, p. 49 

 and »Vid. Medd. Nath. Forening«, København, 1901, pp. 150 — 152. 



I. PTEROSPERMA Pouchet, 1894. 



55. P. Mobii (Jorg.) Ostf. , Vid. Medd. Nath. Forening, Køben- 

 havn, 1901, p. 151; Pterosphaera Mobii Jorgensen, Bergens Museums 

 Aarbog, 1899, VI, p. 48. 



Very rare around the Færoes, only found twice in a few specimens 

 in winter (February— March). A temperale, oceanic organistn which ap- 

 pears every winter in the North Atlantic Ocean. 



56. P. Vanhoffenii (Jorg.) Ostf., 1. c. p. 151; Pterosphaera Van- 

 hoffenii Jorgensen, 1. c. p. 48. 



Occurs togethcr with the above-mentioned species, but is not so rare; 

 found in 6 samples of October and January— March. Has the same 

 distribution as the species mcntioned above. 



57. P. dictyon (Jorg.) Ostf., 1. c. p. 151; Pterosphaera dictgon 

 Jorgensen, 1. c. p. 48, PI. V, ligs. 27, 28. 



Only one specimen met with (October). 



58. P. labyrinthus n. sp. 



Cell spherical, lamellae (wing-lists) form few and large meshes, 



with undulating sides; lamellae 

 consisting of two closely-lying 

 layers, which ultimately separate; 

 in the optical section the two layers 

 are seen as two lines which are 

 parallel in the main part, but di- 

 verg at an obtuse angle in the 

 upper; seen from the surface the 

 meshes are broad and with a cir- 



cular dot where thrce meshes meet. Diameter of the whole or- 



ganism about 60 p, of the cell proper aboul 28^. 



Only two specimens occurred in a sample of March 1901. 



Fin'. 127. Pterosperma labyrinthus Ostf., n. sp. 



Cell in optical view and the same seen from the 



surface ( ri ""/i). 



II. HEXASTERIAS Cleve, 1900. 



59. H. problematica Cleve, K. Sv. Vet. Akad. Handl., Bd. .'59, No. 8, 

 p. 22, lig. C). 



I think that the little-known organism which Professor Cleve 



