KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 34. \:o 2. 23 



P. pellncidum Bergh. — April, May: follows /'. ovaturn in the North Sea, bal rarer; 

 Plym. rr; Måseskär r. July: Grullinarfjord r. August: Orkneys r. 



P. yexans Mukkay A; Wmitting. — June, August: Plym. rr. 



Pyrophacus horologinm Stein. - February: North Sen, rare among tripos-plankton. 

 July, August: Shetlands r; E. of Scotland r; Skagerak r. September: Helder r; Skagerak r. 

 November: a1 sorae spöts between Scotland and the Skagerak. 



Cystae. 



Hexasterias problematica Cl. — March: Helder r. 



Xanthidinm brachiolatum Möb. — July to September: Skagerak rr. 



X. hystrix Cl. — Janna///: Maseskär rr. May: Plym. r; S. of Norway rr. June: 

 Plym. rr; Skagerak rr. July, August: Plym. rr; W. Skagerak r. 



X. mnltispinosiini Möb. — May: 55 X. 6° E. r; Måseskär r. August: W. and E. 

 Skagerak r. November: off the Dutch coast and in the centre of the North Sea r. 



"tv 



Flagellatse. 



Phaeocystis Pouchetii Lagh. - - January and February: St Vaast r +. April, May: 



61° N. L°E. to 58° N. 3° E. ccc; 58° N. 2° E. r; 56° N. 4° E. r; 56° N. 6° E. c; Helder ccc; 

 Plym. ccc +. June: Helder ccc. September: Helder + c. 



Dinobryimi pcllnndnm Levander. — April: Väderö cc\ Måseskär +. May: Måse- 

 skär r. 



Diatomaceae. 



Achnantb.es tseniata Grun. - — February: Väderö rr. 



Actinocyclus Ehrenbergii Ralf. — Mareli: N. of Scotland r. June: Skagerak r. 



Asterionella japonica Cl. — February: St Vaast r. March: Helder rr; St Vaast c +; 



Plym. rr. April, May: NE. of Scotland r; Plym. cc; W. of Denmark, common between 

 55° — 50° N., thence rarer to Skagen and into the Skagerak. August: Plym. cc. October: 

 Skagerak rr. 



Bacteriastrnm varians Lauder. — , July: off Heligoland cc. September: Helder r. 

 November: \V. of Jutland r. 



