E. Ja -gens 



C. exceutriciis Ehkb. 



The form which occurs in the plankton fi'om the northern 

 coasts of Norway, is the typical one which is figured in Schmidt's 

 atlas, (L. 128), pi. 58, f. 49. 



Distribution: Appears to be a northern temperate oceanic 

 form. On the west coast of Norway it is found all the year round, 

 but only occasionally in somewhat greater number. The same seems 

 to be true of the northern coasts, at any I'ate in the months 

 February— May. Othenvise widely distributed along the coasts of 

 the Atlantic, the North Sea and Skagerak right up to Greenland and 

 Jan Mayen. Has, according to more or less reliable statements, a 

 nmch wider distribution and is perhaps cosmopolitan. 



C. lineatus Ehrb. 



The easily recognizable form which is figured by Van Heueck 

 (Synopsis, L. 88) t. 131, f. 3, I hardly think occurs on our coasts. 

 But rarely one finds a form with fine structure and moi-e or less 

 straight secondary curves, which I have entered in the plankton 

 tables under the name of C. lineatus var. I am, however, partly 

 inclined to think that the specimens I have observed may be forms 

 .of (Joscinosira fokichorcla Gran. Cfr. remarks concerning this species. 



Distribution: The genuine C. lineatus Ehrb. is perhaps only 

 found fossil and in the warmer seas. 



C, decipiens Grun. 



Vide Thulussiosira gcJatinosu. 



C. ciirvatiilus Grun. 



Rare on the coasts ot Noiway, occasionally more frequent in 

 the northern coast plankton. 



Distribution : Occurs in many forms, which taken as a whole 

 have a wide distribution. It seems to be frequent on the arctic 

 coasts. (Greenland, Jan Mayen and Franz Joseph's Land). Is 

 pciiiaps an arctic and boreal oceanic form. 



C. stellaris Hop. 



Rare on tlie northern coasts of Norway. Does not appear to 

 belong to the diatom inflow, ami is mostly found singly in deep 

 water samples. 



Distribution : Rare on the coasts of the Atlantic and the 

 arms of the sea in connection with it. On the west coast of 

 Norway most abundant in the winter. Also known from the Me- 

 diterranean. The appearance of C. stellaris in the north, suggests 

 tiiat this species is a tempei'ate Atlantic one (and probably oceanic.) 



Note. C. si/mbolophorus Guitn. (L. 83, p. 82, pi. 4, f. 3—6) 

 is a very nearly related species with considerably coarser structure 

 and difi'erent distribution. According to Rattray (L. 124, p. 493) 

 transitional forms to C. stellaris occur. C. symbolophorus is an arctic 

 and antarctic species (also known from several fossil deposits), which 

 occurs on the west coast of Norway during the inflow of diatoms 

 together with arctic species. In the northern plankton I have also 

 seen it once: "A 1900, Foldouijord, — 100 m. 



C. biocitlatus Uuun. 



Gkfn. I.. 83, p. 55, pi. 3. f. 30. Cleve I.. 26, p. 10, t. 2, 



f. 13. Thalassiosira b'weulatu (Ghun.) Ostenfeld L. 116, p. 

 504, f. 120, 121 (?). 



This beautiful species, which does not seem to have been found 

 before on the Scandinavian coasts, occurred in several of the samp- 

 les, especially in 1900, sometimes rather numerous. It is only found 

 during the inflow of diatoms in the spring months. 



It is probable that this is the same species which is mentioned 

 by Ostenfeld from the Faeroe Islands (1. c), and which he has 

 found in chains similar to those of Ihalassiosira, for which reason 

 he refers the species to this genus as a new subgenus, Coscinolau- 

 deria. 



I have not followed Ostenfeld's example, partly because the 

 genus Thulussiosira is getting to be rather heterogeneous and unnatural 

 on account of the newer elements which have been added to it, so 

 that there will soon be nothing left as a reliable distinguishing 

 feature except the mucilaginous thread; partly too because I have 

 not met with any such chains in my material, in which the species, 

 however, never occurred m any important quantity. Perhaps we may 

 be speaking of two different species, although Ostenfeld's figure 

 considerably resembles our species. (The only thing which seems 

 foreign to it, as far as I can see, is the apiculi which are closer 

 and smaller than in our form, and also the lower cells, as I have 

 only seen high ones). 



Distribution: Arctic and boreal, according to Cleve (arctic) 

 neritic species, known from the coast of North Siberia, ice near 

 Novaja Zemlja, Greenland, the Faeroe Islands (April— May rare, 

 Aug.— Sept. 1902 numerous, according to Ostenfeld, 1. c, who 

 also mentions it from several places in the N. Atlantic). 



Note. Coscinodiscus polyacanthus Geun. (L 48, pi. 7. f. 127) 

 is a little known and somewhat doubtful species, which occurs on 

 the North Siberian coast and at Franz Joseph's Land. In a sample 

 from Folstad, *U 1899, 0—3 m., I found very sparingly a species, 

 which in every i-espect seems to agree with authentic specimens of 

 C. iwlyacanthus from Jamal (Swedish expedition to Jenessey 1875, 

 slides in possession of the Riksmusæum, Stockholm I. (Cfr. under 

 Coscinosira polychorcla). 



C. polyacanthus Grun. var. intermedia Grun. (1. c. p. 81, pi. 

 3, f. 25) is probably another species, if it does not belong to C. 

 curratulus (it has, like this species, interfascicular apiculi). Speci- 

 mens quite answering tn the figure and description of Grunow were 

 found sparingly in a sample from Skjerstadfjord XII, ""A 1900, 

 — 500 m. Known from Cape \\'ankai'ema. 



C. radiatns Ehkb, 



Exceedingly variable. Theie are, however, certain distinctive 

 marks by which all forms belonging to this species can be recog- 

 nized. Gran (L. 70, p. 166) has already well characterized this 

 form: — low („coinshaped") cells, flat valve, markings near the 

 border suddenly voi y smnll. 



■ The larger lonns have a distinct central rosette and often 

 areoles, which increase in size nearly up to the border, and are then 

 C. oculus iridis. Ehbb., as this very much disputed species has been 

 described by Grunow and Rattray. From these forms (cfr. 

 Schmidt's atlas, (L. 128) pi. 63, f. 6., which form, however, has 

 larger marginal areoles than usual) there seems to be every transi- 

 tion to the ordinaiy C. ruil'ialus witJiout the central I'osette and with 

 markings which aic of about the same size nearly up to the bor- 

 der. Grunow (L. 83, p. 25) also observes that C radiutus passes 

 into C. oculus iridis, but it must be mentioned that he seems to 

 give little or no weiglit to the convexity of the valve (when this 

 is not particularly conspicuous), and therefore he classes together 



