ItliailMloiit'iiiii KiTZ. 

 R. miinitum Knz , K. iircimtuiii (I.VNOii.) Kit/, iin.l K. iiilriiiticiim KiTZ. 



Nut tri'uuiiie plankton I'onns. most likely by iiceidunt brought 

 alonsr tVom tixeci al^ae. 



Striatflla unijniueUitn (Ly.nob.) Ao. 



Very rare and scarce. The Vest Fiord '/a 1H99, 0—200 m., 

 the Ogs Fiord II, '^3 1899. (i— 200 m., and the Skjerstad Fiord 

 V, 'A 1900, 0-420 in. 



Hardly a genuine plankton fonn, by chance brought in from 

 fixed algae. 



D'lstr'iliui'niH : Widely distributed along the temperate coasts 

 of the Atlantic. .\lso mentioned from Finmai'k, where it, however, 

 to judge from the bottom samples, api)ears to be rare. 



JO. Nitzschieæ. 

 Raeillariii sucialis Greg. 



Greg. L. 75, p. 8u, pi. 1, f. 45. VH. Synopsis (L. 88), pi. 

 61, f. 8. 



(Wrongly entered in the tables as B. paradoxa). 



Not a genuine plankton form. Only very sparsely and quite 



exceptionally noticed in the plankton. Frequent in the bottom 

 samples. 



Diatribtition : The coasts of the Atlantic from Portugal to the 



arctic regions (Sea of Kara). Also mentioned from the Baltic and 

 the Antilles. 



\it7,!iicliia Hass. 

 N. seriata Cl. (includinj; A', frandulftita ('l.) 



Only found during the inflow of diatoms in spring, then almost 

 always frequent, and often numerous. 



Distribution: Arctic and boreal species. It seems to be a 

 neiitic species, which may perhaps be native to our west coast 

 where it is found more or less abundantly during most months (of 

 1898), often in quantities, most numerous in May— June. Ofif the 

 Faeroe Islands generally very sparsely, but numerous in June 1898. 

 Also known from Greenland, Spitzbergen and the Barents Sea 

 (S/S Heimdal 1900, -'A, 71" 48' n., 49" 38' east, sparsely). Cfr. 

 Ci-EVE L. 40, p. 335, where he mentions the species as being 

 specially distributed between Scotland, Iceland and Greenland. He 

 also (1. c.) mentions that var. fraudulcnta is known from the 

 Mediterranean. It is therefore probable that there are two species ; 

 the one, N. fraudulentn Cl. having a southern distribution and 

 being probably oceanic, while the other is neritic and arctic. 



A', delicatissima Oi,. 



Cl. L. 27, p. 24, pi. 2, f. 22. 



This species is so small, more particularly so narrow, that it 

 must be supposed as a rule to go through the net. In the plank- 

 ton material at my disposal it has certainly in the majority of cases 

 been retained by the colonies of Phæocyctis. 



Like the preceding, only found during the inHow of diatoms 

 in .spring, then fre(|uent, and in all probability much more so than 

 would appear from the tables. 



Distrihutiou: Probably, like the preceding sjiecies, really an 

 arctic, neritic species, which, however, seems to thrive in the water 

 mixed with the warmer Atlantic .\lso, like the preceding species, 

 found off the Faeroe Islands. Known too from Spitzl)ergen and 

 Skagerack where it occurs in winter. At Ona (cfr. (Jhan I^. 70, 

 p. 181) frequent in June— July 1900. 



N. hyhrida «bin. 

 (PI. VI, Hk. 12). 



('i,, and (iui N. L. is. p. 71i. pi. .■), f. '.t5. \'ll. Synopsis (L. 

 8H) pi. (iO, f. 4-5. 



I have included, undei- this heading, a number of forms which 

 frequently occurred during the inflow of diatoms in the spring of 

 1899 and 1900, although generally only in small numbers. They 

 are not in every instance entered in the tables, and are consider- 

 ably more frequent than would appear from them. Seems to be 

 a genuine plankton form. I have illustrated some of these forms 

 (PI. VI, tig. 12). Figure 12 a represents those wliich are most fre- 

 quent, but they are most often less distinctly constricted in the middle, 

 often of an even breadth. 



Strise I have only seen on the one illustrated by flg. 12 e (about 

 27 on 10 iJ.) which differs considerably from the ordinary form, also 

 in the number of puncta on its keel (13 on 10 |i). 



The closely allied species A', (lu/hrida var. ?) peUucida Grun. 

 has the puncta on the keel somewhat closer (13-14 on 10 |i) but 

 in otliPi- icspects it answers better to the forms which I have ob- 

 served. 



Geunow mentions (1. c.) that there are a number of intermediate 

 forms, which it is difficult to define, between .V. hilohnta and -V. 

 hyhrida. All my forms have the keel puncta more widely separa- 

 ted in the middle; they are often comparatively long and there 

 is a decided trace of a central nodule. The keel appears to be 

 very eccentric — 1 have, however, only in a couple of instances 

 seen the species in valvar view, cfr. fig. 12 d — so that there 

 seems to be a connection with the forms which are related to A'. 

 duhia W. Sm. 



Seems to be a genuine plankton form. It is (with us I only 

 slightly siliceous and often occurs in pairs, (juite rarely also in short 

 chains of several links. 



Distribution: Aictic and boreal coast form. Known from 

 Greenland, Spitzbergen, the Barents Sea, (S/S Heimdal 1900, ",;. 

 71" 48' n., 49" 38 east, in small numbers, the same form as with 

 us) and the Kara Sea. Cfr. 1)k Toni (L. 50, p. 513) who men- 

 tions it as occurring also on the coasts of Great Britain. 



N. hilohata W. Sm. 



W. S.M. L. 134, p. 42. pi. 15. f. 113. VH. Synopsis p. 175, 

 pi. GO. f. 1. 



Occurs very seldom and only singly. Hardly a true plank- 

 ton form. 



Distrihittion : Widely distributed on the temperate European 

 coasts of the .\tlantic. 



iV. frigida Grit;. 



Cl. and Gkln. L. 48, p. 94, pi. 5, f. 101. 



Rather rare and always in small numbers, there is a form 



