Protistplanktoii. 



remarkable eoiitents of the cells of .V. ]'ii)ihoff'ciii are at any rate 

 not found here. 



Achnanthes hypeiborea Grun. is a puzzlingly similar species. 

 (^RiNow mentions too that Stanroneis scptentrioiialis mi^fht pei'haps be 

 the lower valve of an Achnaiithes. It appears, however, that he, both 

 in this instance and with regard to Achnanthes tæniata, at once 

 came to the correct conclusion. 



As before mentioned, Achnanthes hyperhorea was also found 

 in the sample from the Barents Sea, but only in small numbers. 



.Tudginy' from my experience, it would seem possible that there 

 is yet another species, answeriHg to N. septentrionalis Oestk., to 

 be found in the bewildering wealth of species in the arctic, neritic, 

 diatom plankton. As, however, the ditference between Oesteup's 

 species and Stanroneis septentrionalis seems to be so slight, I have 

 thought it best at any rate for the present, to consider tiiem to be 

 synonymous. 



Stanroneis Grant Jorg. n. sp. 

 (PI. VII, fio;. 25). 



Forms chains in which the cells touch each other except to- 

 wards the ends, where the cell in side view appears to be narrowed 

 off uniformly (outlines arched). 



On being ignited on cover-glass, the connection is still further 

 severed, so that the cells only touch each other in their middle 

 half (more or less). The ends are sharply bent so that the cells 

 of the chains in material preserved in alcohol look as if the ends 

 were cut off in a straight line by a sharp knife. 



There is a small central stauros, bounded by two parallel lines. 

 No other structure was seen on the valve. 



The connecting zone complex as that of Xnrirula Yanhoffcni. 

 As in the latter species, the connecting complex membranes are 

 seen between the ends of the cells. They are, however, as a rule 

 rather indistinct. 



The contents of the cell are generally speaking the same as 

 in Xavicida Vanhoff'eni, with which species Stmroneis Grani is 

 very nearly related. 



Length .54—57 |i. 



I have not been able to identify this species with any of those 

 hitherto known. It may perhaps be the same as that which 

 Gran L. 70, p. 147, mentions from the Barents Sea, ^'A 1900, as 

 Xaiiciila septentrionalis. It does not, however, appear to be iden- 

 tical with the one which he mentions from Greenland L. 65, p. 9, 

 as the above species is considerably larger. 



Moreover, the only species with which, according to my opinion, 

 it would be possible to unite it, would be Statironeis pdlucida Cl., 

 which species is mentioned by Cleve from Cape Wankarema (L. 

 45, pi. 35, f. 10). Cleve's illustration, however, resembles it very 

 little; the species is though, according to Oestrup (L. 138, p. 440) 

 exceedingly variable. 



Occui'red singly in one sample: Poi'sangerfjord, -'ji 1899, 

 — 75 m. 



Distrilmtion: Hitherto otherwise only known from the Barents 

 Sea, 71» 48' n. lat., 49» 38' e. long. (S/S Heimdal "'/s 1900). I 

 have also seen a short chain from the Kara Sea (the Swedish 

 Jenissei expedition, 1875). In this slide, tiiere was also a short 

 chain of the species which 1 have entered as Stanroneis septen- 

 trionalis (iiu-N. 



Sriiiy.ononia (irevillvi An. 



Only by accident brouglit in with liigliei' algae. Common 

 amonii' bottom algao on tiio west coast of Norway. 



l*l<'iirwsiU'iiiii W. Ssi. 



P. angulatum (Quek.) W. Sm. and P. Normanni Ralps (= P. affine Gkin.) 



Not genuine plankton forms, only accidentally brought in. 

 The latter species is very frequent in l)ottom samples. 

 Also occur now and then singly in the plankton P. formosum 

 W. Sm. and P. balticum (Ehhb.) W. Sm. 



P. tenerum Jorg. n. sj). 

 (PI. VII, rig-. 17). 



P. Stiixbergi Cl. L 48, p. 54. pi. 4, f. 74 (?). 



Under this name, a species is entered in the tables which cer- 

 tainly is a genuine plankton form, as in some of the samples 

 (Rombakeu 72 and Skjomen Va 1899) it was quite common, and 

 occasionally occurred in large quantities. It was also now and 

 then found durhig the inflow of diatoms in the spring, especially 

 in 1900, but then always in small numbers. 



The species corresponds so well, in all important points, with 

 P. Stuxbergi Cl. and Grux., that I have been in doubt as to 

 whether or not it should be entered under that name. Finally 1 

 came to the conclusion that I ought to do so, as will be seen on 

 reference to the tables for 1900. 



There were, however, chiefly three things which made me 

 provisionally enter it as a separate species. First, because it is 

 one of the few species of Pleurosigma which is really planktonic; 

 secondly, it is very thin walled and is easily deformed when ignited 

 (a fact not mentioned with regard to P. Stuxbergi) and Anally, 

 Cleve classifies his species under the di\1sion Ehoicosigma (L. 24, 

 p. 41), while I was convinced by examination of preserved material 

 that, seen in side view, it is not bent. 



When ignited on cover-glass, it loses — as already mentioned — 

 its shape, and I have often seen specimens which, after being 

 treated in this way, give the impression of being a Rhoico- 

 sigmu. 



Distribution of P. Stuxbergii: Greenlanil, Frantz Josepli's Land, 

 Kara Sea. Probably an arctic coast form. 



P. delicatiilum W. Sm. 



(PI. Vir, a-r. 18). 



\'ery like P. kurianum Grun. L. 48, p. 50, pi. 3, f. (59, 

 wliicii is referred as a vai'iety to P. delicatulum W. Sm. by Gru- 

 Now with some doubt, and to P. elongatnm W. S.m. by Cleve. It 

 is also veiy like P. fallax (Grun.) Perag., which is considered a 

 variety of P. ehngatum both by Cleve and Grunow. These forms, 

 however, all ditfer from the one obsei-ved by me by the transverse 

 striæ being closer than the oblique ones, while the contrary is 

 rather the ca.*e in my form. 



Very rare: *U 1899 Folstad, 0—3 m. \'ery closely allied 

 forms also occur, but always very sparsely (and only during the 

 diatom inflow I. 



