34 



P. T. CLEVE, THE PLANKTON OF THE NORTH SEA, ENGLISH CHANNEL, ETC 



Tintinnus acuminatus. — Nov. 



Plectophora arachnoides. — Nov. 



Dinobryum pellucidum. — April. 



Achnanthes seriata. — Febr. 



Chcetoceros constrictus. — Febr., April, May. 



C. contortus. — April, May. 



C. diadema. — Febr.; Sept. — Dec. 



C. hiemalis. — Febr., May. 



C. scolopendra. — Jan. to May; Sept., Nov. 



C. seiracantha. — Mareh; Nov. 



All are arctic or northern species. 



The following are of southern origin 

 Microsetella atlantica. 

 Ceratium lineatum. — 

 Rhizosolenia gracillima 



C. socialis. — Febr., March; Nov. 

 Coscinodiscus polychordus. — Febr., April; Nov 

 C. stellaris. — Febr. March; Nov. 

 Leptocy lindrus danicus. — April, May. 

 Nitzsclda seriata. - — Febr., May. 

 Rhizosolenia semispina. — Jan., May. 

 Thalassiosira gravida. — Febr., May. 

 T. Nordenskiöldii. — Jan. to May. 

 Thalassiothrix Frauenfeldii. — Jan. to May. 

 T. longissima. — Jan. to May. 



— June. 

 Febr., Jnly. 

 — May to December. 



