Diatom 



197 



Border sharply defined, dark, striate. The disc somewhat convex 

 towards the border. 



The specimen found only differs from Schmidt's figure in 



wanting the ..central space". Instead of this space, which is, how- 



- ever, not mentioned by Rattray 1. c. a large areole was present. 



Distribution: Pacific Ocean, especially in the northern region 

 (Kamtschatka Sea. Hailey). Cape Wankarema (Cleve). 



C. decrescens Grin. 

 Gkdn. Diat. Franz Jos. I, ami. p. 28. A. Schmidt Atlas, pi. 61, figs. 7—9. 



B \ i i;.\v 1. c. p. 77. 



Perhaps a plankton form, occurring with us like C. subbulliens. 



Coarse structure, conspicuous ..papilla". Recognizable through 

 the rapid decreasing of the areoles outside of 7s radius. 



Rare: Moskenstrommen r+, Stamsund r. Diameter 92 |i or 

 less; largest areoles somewhat outside of 7s radius, 2 on 10 \i, at 

 the centre smaller, on the border much smaller. Border broad, 

 sharply defined, striate, with 5 — 6 striae on 10 \k Central space 

 generally absent (answering to var. repleta Geun. 1. c), sometimes 

 present. 



Distribution: Faroe Channel. Franz Josef's Land. Japan, 

 Macassar Straits, Florida. 



C. radiatus Ehrb. 



Cf. above p. 92. 



Probably derived from the plankton. 



Rather frequent: Moskenstrommen c Stamsund r +, Svolvaer 

 r. 0stnesfiord r. Gaukvaero -f-, Stene r. 

 Distribution : Cosmopolitan. 



var. minor A. Scum. 

 A. Schm. Novels. Diat. p. 94, pi. 3, f. 4. C. devius A. Schm. Atlas, pi. 60 



figs. 1 -4. 



Stamsund r. Svolvaer r. Oaukvaro r, Stene r. 



var. oculus iridis (Ehrb., Eattr.). 



Flat. A conspicuous central rosette and often a small „central 

 space". Areoles largest at or beyond 1 / 2 radius, hexagonal, with 

 large ..papilla", towards the border rapidly decreasing, at the very 

 margin small. Largest areoles 3 on 10 \l. 



This form, which answers very well to Coscinodiseus oculus 

 iridis Eheb. Mikrogeologie pi. 19, fig. 2, is certainly not specific- 

 ally distinct from C. radiatus, intermediate forms being rather 

 frequent. 



Moskenstrommen r, Gaukvaero r. Occurred also in other 

 samples. 



C. nodulifer Jan. 

 •Tamsch. in A. Schmidt Atlas, pi. 59, f. 21. 



Flat. A small, but conspicuous nodule near the centre. Are- 

 oles hexagonal, increasing from the centre to 7 4 radius, here :S on 

 1" !'.; towards the margin rapidly decreasing, at the border 5 — 6 

 on 10 (jl. Border sharply defined, striate, with 6—672 striae on 



10 |JL. 



Answers very well to the figure referred to. 

 Rare: Raftsund +. Brettesnes— Skroven r. 

 Distribution: This southern species is found near the Balearic 



Islands and in the wanner regions of the Atlantic. Pacific and In- 

 dian Oceans. 



It is very remarkable that this species occurs so far north. 

 It is probabh a plankton form, most likely a fossil one. 



Actinocyclns Ehrb. 



A. alienus <■ ri n. 



Grin, in Van Hkurck Synopsis, pi. 125, !'. 12 (var. arcticus). 



Very rare: Brettesnes — Skroven r: Stene r. In structure 

 Coseinodiscus-]ike, as Gbunow states intermediate between C. cur- 

 vatulus and C. radiatus. Central space circular, conspicuous, only 

 with a few irregularly scattered puncta. Numerous fasciculi (over 

 20) with interfascicular radii, which are more or less plainly ziczac 

 bent, especially towards the centre. Towards the margin, the fasci- 

 culi are not separated from each other, but form an even radiately 

 structured marginal part. Very small and inconspicuous marginal 

 apiculi. Border narrow, indistinctly striate. 



Diameter 61 — 66 |jl; rows of areoles 15 on 10 ;>. at the mar- 

 gin closer. Ocellus marginal, evident. 



Distribution: Cape Wankarema. Also mentioned from a few- 

 places of the North Atlantic and Arctic Seas. 



A. Ehrenbergi Hales. 



Cf. above p. 95. 



Probably derived from the plankton. 



Not unfrcquent: Stamsund r. Svolvaer r. Gaukvaero r. Stene -f-. 



Distribution : Cosmopolitan. 



A. Ralfsii (W. Sm.) Ealfs. 



C\\ above p. 95. 



More frequent in the bottom samples than in the plankton 

 (from which however must not be concluded that it is a bottom 

 form): Stamsund r, Svolvaer r-f, Ostnestiord r. Gaukvaero r+, 

 Stene r. 



Distribution: Western Europe. Greenland (0stbup). War- 

 mer Seas. 



Eattr. Revis. Actinoc. 



A. sparsus (Gbeg.) Battb. 

 1890, p. J7o. Eupodiscus sparsus Greg. Trans. Micr. 

 Soc. 1857, p. 81, pi., fig. 47. 



The description by Rattkay does not answer well to the figure 

 referred to. According to this figure, it seems chiefly to differ from 

 A. Ehrenbergi in being more sparsely granulated towards the cen- 

 tre, so that only the interfascicular radii reach the central space. 

 It is, however, doubtful whether it can really be kepi distinct 

 from the preceding species. Also A. moniliformis Rales seems to 

 be a species very closely related to A. Ehrenbergi. 



Specimens which seem to belong here were found in the sample 

 from Gaukvau'o. r. 



A. crassus V. H. 



Van HEURCK Synopsis p. 215, pi. ll J 4. figs. 6, 8. 



Van Heurck's figure shows interfasciculate radii, though not 

 so evident as those of A. Ehrenbergi. Smaller and coarser forms 

 of the latter species is puzzlingly similar to A. crassus. It is on 



