334 с. H. OsTEXi-ELD and Ove Paulsen. 



hyperborea, small quantity of Coscinodisciis subbuliens, Chaet. boréale 

 and Ch. Wighami. 



The intermediate group (5 samples) extends from ca. 12° to 8"" 

 W. L.; here we have a salinity of ca. 31 7^0 and a surface temper- 

 ature of — Об"" to — 1-5° C. It is characterized by the following species, 

 which are hardly at all found inside : Chaetoceras fiircellatiim, Rhi- 

 zosolenia obtusa, Rh. hebetata f. semispina, Dinobryon pelhicidiim, Cytta- 

 rocylis denticulata typica. A few species, which very seldom occur 

 in the inner group, appear here more regularly, namely, Chaet. dia- 

 dema, Peridimum pallidum, P. pelliicidum and P. ovatiim. Thalassi- 

 osira gravida, which was much reduced, again becomes more fre- 

 quent in this region. Most of the species prominent in the inner 

 group disappear here or are only present in small quantity. 



A couple of samples form the transition to the outer group, to 

 which we ascribe the region from ca. 7° to 6° W. L. and from 75° 

 to 73° N. L. The saHnity is here higher (33—34 *Voo) and also the 

 temperature on the surface (6° — 7°) tlian in the other regions; we 

 are here outside the pack-ice. The quantity of the plankton is but 

 small; the diatoms have almost entirely disappeared; characteristic 

 however is the regular occurrence of Chaetoceras convolntiim in small 

 quantities; further, a number of diatoms of more temperate origin 

 appear irregularly and in few individuals and likewise some Pro- 

 tozoa (see our preceding papers). The most abundant organisms are: 

 Peridinium ouatiim, Dinobryon pellucidum, Cyttarocylis denticulata ty- 

 pica and robusta, Oithona and Nauplii, and in most samples Cera- 

 tium arcticum, Tintinnus norvégiens gracilis and Peridinium pyriforme. 

 In a few samples occurred Phaeocystis Pouchetii, Pontosphaera bore- 

 alis and Coccolithophora pelagica. 



The plankton in the outermost samples corresponds nearest to 

 the "Ceratium arcticum plankton", which Paulsen (1909) has 

 described from North Iceland (the southern boundary of which is pla- 

 ced at ca. 64 N. L. in his iig. 2), but ditïers from this in the absence 

 of Ceratium longipes (the С arcticum most resembling longipes is 

 figured in the foregoing paper fig. 16 A). 



A general review о f t h e plankton of the pack-ice and 

 coastal waters, according to the samples examined, would appear 

 somewhat as follows. In the accompanying sketch map the plankton 

 regions and the places of the samples (the figures refer to the Tables) 

 have been marked out. There are three regions. 



1. Innermost the plankton region of the coastal waters 

 (inner group in 1906 and 1908), characterized by diatoms, namely 

 Chaetoceras species, Coscinodiscus subbuliens, Fragilaria oceanica and 

 by Calanus fmmarchicus. 



