6 P. T. CLEVE, PLANKTON-RESEARCHES IN 1897. 



Dinohryum pellucidum occurs in Skagerak and on the Norwegian coast, 60° N. 5° E. 



Ceratium tripos var. longipes rules in the North-Sea and along the Norwegian 

 coast. It occurs sparingly at the Shetlands, is not rare N.W. of the Hebrides, but was 

 not seen at Iceland. 



Peridinium depressum, which seems to me to differ sufficiently from P. divergens 

 to constitute a separate species, appears on the whole to accompany the preceding. 



Asterionella spathulifera Cl. Ostenfeld considers this species the same as A. 

 glacialis Caste., which seems to me also probable, although not sufficiently proved. This 

 remarkable diatom seems to have a station in the fjords of the south of Iceland. It was 

 found abundantly at Helder and in April also at Plymouth. On the other hand it was 

 observed neither on the route Shetlands — Greenland nor along the Norwegian coast. It 

 seems to invade the British Islands in the spring, following the east coast down to the 

 Continental shores of the North Sea. It was found in April 1895 together with other 

 northern forms east of the Wash and, låter, in July, according to a letter from Prof. 

 Beyeninck of Delft, along the Dutch coast in such iramense quantities that it coloured the 

 sea colfee-brown and left on the shore a stratum of one centimetre in thickness, thus 

 representing millions of kilogrammes. At the end of the same month it had disappeared. 



Biddidphia aurita appeared together with other northern and arctic forms in the 

 beginning of April at Helder, from whence it soon disappeai^ed completely. It is not men- 

 tioned from the routes Färöes — Shetlands and Shetlands — Greenland. 



Chcetoceros atlanticus, rare south of Iceland, around the Färöes and west of Scotland; 

 very sparingly on »Reykianäs Ryg». 



C. borealis, not found at Helder and Plymouth. As Ostenfeld has not distinguished 

 between the type and the varieties nothing can be stated about its western distribution. 



C. diadema occurred south of Iceland and abundantly at the Shetlands, but not 

 in the Färöe Ghannel and along the coast of Norway. 



C. hiemalis, found rarely at Cape Stadt in Norway. 



C. laciniosus, not found off Norway but plentiful near the Shetlands and Färöes, 

 sparingly south of Iceland, but abundantly along the 60th degree of lat. between 11° 

 and 37° W. 



C. scolopendra, not found along the Norwegian coast and not on the route Shetlands 

 — Greenland, but sparingly at Färöes. The same may be said about C. teres. 



Corethron liystrix was found in February at Plymouth, in March off the Hebrides, 

 but not along the Norwegian coast. This species belongs to the styli-plankton. 



Coscinodiscus oculus iridis occured very sparingly along the Norwegian coast, was 

 not rare on the route Shetlands — Iceland nor off the south-west of Greenland. 



C. polychordus was seen in March at the Hebrides, not along the Norwegian coast 

 and is not mentioned by Ostenfeld. 



Lauderia annulata belongs to the styli-plankton and is derived probably from West 

 Scotland, where it was seen in the autumn of 1896. 



NiUschia seriata was not seen off Norway, but plentifully at Färöes. It was also 

 seen abundantly along the 60th degree of lat. from 11° W. to the »Reykianäs Ryg». It 

 follows Chcetoceros laciniosus. 



