104 



which coi responds to the illustration mentioned whei-e there is ijixeu 

 a front view of this species. Besides typical forms, others also 

 occur which are hardly any broader in the middle. 



I have not seen this species in valvar view. It seems unlikely 

 that my species should have the characteristic form of valve as 

 illustrated by Oestrup, L. 1.38, pi. 8, f. 99 a— e. 



Distribution: Arctic, neritic form, known from Greenland, the 

 Barents Sea and the Kara Sea. 



N. arctiea Cl. 

 (PI. VI, fig. 1.5). 



Cl. L. 26, p. 21, pi. 1, f. 21. 22. 



Rather frequent, but always in small numbers, there occurs a 

 species wliich it has been difficult to determine with certainty. 

 It was noticed both in 1899 and 1900, but only during the 

 inflow of diatoms, and is only entered in the tables for 1900, under 

 the name of N. recta Hantzsch, which is, however, a wrong' one. 

 I thought afterwards that it might perhaps be a straight form of 

 the high arctic species N. lævissimu Grun., but finally held to the 

 designation ^V. arctiea Cl. 



I have also here observed a number of forms which are more 

 like each other- than the corresponding ones of N. hyhrida. 



The keel is very eccentric, the puncta very Uttle lengthened 

 in width, 7V2— 10 on 10 |i, the two in the middle being more widely 

 separated and there is a ti-ace of a central nodule. The valve is narrow 

 lanceolate, acuminate. 



The cell in side view is long and narrow, linear, somewhat 

 broader in the middle, with truncate ends. The connective zone 

 longitudinally striated. 



Varies much in length, 60—100 ij., the cell is 7—12 \i. broad 

 in side view, the valve 4—5 |j. broad. 



Strangely enough no striæ were to be seen. All the specimens 

 I examined were, however, thin walled. 



Seems to be with us a true plankton foi'ui. 



Distribution: On the north east coast of Siberia (Cape Wan- 

 karema) and Da\1s Strait. Probably an arctic coast form. 



N. angularis W. Sm. 



(PI. VI, fig. 14). 



\V. Sm. L. 134, pi. 13, f. 117. VH. L. 88, p. 177, pi. 62, 

 f. 11-14. 



Not a true plankton form. Cfr. the chapter on bottom samples. 



Rare and scarce dui-ing the diatom inflow a little form occurred 



(PI. VI, flg. 14, a, b), which answci's well to A^. angularis 

 var. karlana Grun. (L. 48, p. sy, pi. .5, f. 100). Length 36— 

 54 |i.. 



(Lille Molla, 'A 1899; Seivaagcn, Vj 1900). 



A'. spalhtilatH Breb. 



Lkki;. in W. Sm. L. 134, I, p. 40, pi. 31, f. 268. VH. Synopsis 

 (L. 88), p. 177, pi. 62, f. 7 — 8. 



Very rare and only singly. 



Not a genuine plankton form. Occasionally found in bottom 

 samples. fCfr. the cori'csponding chapter). 



N. lanceolata W. Sm. 



W. Sm. L. 134, I, p. 40, pi. 14, f. 118. VH. Synopsis (L. 88), 

 pi. 68, f. 1—4. 



Like the pi-ecedinff species. 



PI. VI, fig. 13 represents a very small form, which answers 

 very well to A'. lanceolata var. p/jgmaea Cl. L. 45, p. 481; L. 

 26, p. 22, pi. 1, f. 19, 20. 



Length 30 |j., breadth 4 [i.. The keel puncta are small and 

 close together, about 14 on 10 |jl, the two middle ones more vndely 

 separated, with a trace of a central nodule between them. 



Tills form which occurred '/* 1899 Lille Molla can, however, 

 hardly belong to N. lanceolata on account of the keel puncta being 

 so close together and also because of the distinct trace of a cen- 

 tral nodule. Cleve mentions this form from Cape Wankarema and 

 Davis Strait. 



N. longissima (Breb.) R.^lfs 

 Rai-e and occurs only in small numbers. 



N. closterinm (Ehrb.) W. Sm. 



Of very rare occurrence in the samples. 



It does not seem possible always with certainty to distinguish 

 between this species and X. longissima. 



Hardly a genuine plankton form. 



Distribution: Common temperate coast form, widely distributed 

 on the coasts of Europe. 



N. Mitcbelliana Greexl. 



Greenleaf L. 73, p. 107. 

 Only noticed a couple of times. 

 Not a genuine plankton form. 



II. Siirirelleæ. 



^inriri'lla Turp. 



S. tastiiosR Ehrb. and S. lata W. Sm. 



are not genuine plankton forms. Cfr. the chapter on bottom samples. 



CampylodiMciiK Ehrb. 



C. Thuretii Breb. and C angularis Greg. 



occur frequently in plankton samples and now and then not in 

 small numbers, but they must, nevertheless, without doubt be looked 

 upon as 'being accidentally brought in, as they are rather com- 

 mon in bottom samples. 



C. Ealfsii W. Sm. is also rather often found in plankton 

 samples. 



12. Cocconeideæ. 



<'0<M'OIIt'lx EllRB. 



C. .«iciitellnm Khrb., C. pinnata Greg, .ind C. costata Greo. 



occni' only seldom and singly in plankton samples, and are probably 

 accidentally brought in from fixed algae. 

 (Refer to bottom samples). 



