1 96 



E. Jorgensen. 



specimen agrees completely with Coscinosira polychorda Gran, but 

 wants the peculiar transverse processus of the latter species. 



Such forms, which are perhaps solitary cells of Coscinosira, 

 may easily be mistaken for C. lineatus. 



Distribution: The main species is cosmopolitan, ('leak and 

 0steup mention C. lineatus from several arctic localities: Finmark, 



Baren Kil 1, Greenland, Spitzbergen. Kara. 1 should, however, 



think that the species has been confounded with Coscinosira poly- 

 chorda, at any rate to some extent. 



C excentricus Ehrb. 



Cf. above p. '.H'. 



Frequent: Moskenstronnnen r, Stamsund +. Gaukviero r -f-. 

 Derived undoubtedly from the plankton. 

 Distribution: Cosmopolitan. 



C. Kiitzingii A. Schm. 

 A. Schm. Atlas, pi. 57, f. 17. C. marginatus A. Schm. Nords. Diat. pi. 3. f. 35- 



As Grtjnow remarks, this species is intermediate between C. 

 • ccentricus and the difficult group of C subtilis. 



Very rare: Raftsund r, Stamsund r. 



Distribution: North Sea. Arctic and antarctic regions (Grin.). 

 Not mentioned by Cleve as arctic. Very nearly related forms 

 are found near Greenland (C. a&umbratus 0str.) and Jan Mayen 



(1898, E. J0RGENSEN). 



C. Rothii (Ehrb. V) Grun. 



Grin. Diat. Franz Jos. Land, p. 29. pi. Ill ((.'), figs. 20 a, b, 22. C. st/mtiie- 



tricits A. Schm. Atlas pi. 57, tigs. 25 — 27, non Grew Heterostephania Rothii 



Ehrb. i. octonaria Mikrogeolouie 35 A. XIII B, fig. 4 a. 



Belongs to the difficult group of C. subtilis Ehrb., as well as 

 the following species and a good many more, which probably will 

 not bear a more thorough examination. 



Structure plainly fasciculate, with numerous fasciculi separated 

 by radial lines made conspicuous by the marked inner ends of the 

 beginnings of new rows. Small marginal apiculi in the middle of 

 the fasciculi, one in each. Valve almost flat (occasionally undula- 

 ted according to Grunow). 



Very rare: Stamsund r, Raftsund r, Brettesnes — Skroven r. 

 Probably a plankton form. 



Distribution: Belgium, Scotland; Caspian ^ea. Warmer re- 

 gions of America and Asia. Southern Seas. 



C. Normanni (Ires. 



Greg. Quart. Journ. Micr. Sc. 1859, p. 80, pi. 6, fig. 3. C „normanicus" Van 



Heukck S3'nops. pi. 131, I. C. fasciculahts A. Schm. Nords. Diat. pi. 111. figs. 



41, 42: Atlas pi. 57. figs. 9, 10. 



Very closely related to the preceding species. Differs in hav- 

 ing a distinctly convex valve, finer structure (though variable in 

 this respect), more numerous and narrow fasciculi and less distinct 

 marginal apiculi. 



It is perhaps not quite certain that this species is identical 

 with C. Normanni Greg.; the name C. fasciculatus A. Scum. (1874) 

 must however be abolished on account of C. fasciculatus O'Meaba 

 (1867). 



This species seems to me to answer tolerably well to C. %mnc- 

 tulatus Greg. In specimens with tine structure the fasciculi are 

 only seen with difficulty, while the clear, scattered dots mentioned 



by Gregory 1. c. are conspicuous. If this should prove correct, 

 the C Normanni Greg, is perhaps the same as C. Rothii Grun. 



Rather frequent: Stamsund r 4-, Svolvser r -+-, Brettesnes — 

 Skroven r, 0stnesfiord r -f-, Stene r. Probably a plankton species 

 (living or fossil). 



Distribution: Western Europe. America. Arafura Sea. 



C. curvatulus Grun. 



Cl\ above p. 92. 



Derived undoubtedly from the plankton. 

 Very rare: Stene rr. 



Distribution: Arctic regions; Northern European coasts; Ba- 

 learic Islands. America and Africa. 



C. stellaris Eop. 



Cf. above p. 92. 



Derived undoubtedly from the plankton. 



Very rare: Gaukva-ro r. When the conspicuous star is want- 

 ing, the species is difficult to determine. 



■var. symbolophorus (Gbun.). 

 C. symbolophontS GRUN. Diat. Franz Jos. Land, p. 82, pi. IV (D), figs. 3 — fi 



Differs from the main species in having much coarser structure. 



Very rare: Moskenstronnnen r. Raftsund r. Like the main 

 species planktonic. 



Distribution: The main species occurs in Western Europe, the 

 Mediterranean and the antarctic regions, the variety in the arctic 

 and antarctic regions. 



C. concinnus W. Sm. 



Cf. above p. 93. 



Derived undoubtedly from the plankton. 

 Very rare: CaukvaTO. rr; Stene, r. 

 Distribution : Cosmopolitan. 



C. centralis Ehrb., Rattr. 



Cf. above p. 93. 



Derived probably from the plankton. 



Not unfrequent: Moskenstronnnen r. Stamsund r, Raftsund r. 

 Stene r. 



Distribution : Cosmopolitan. 



C. subbttlliens Jsjrg. 

 C. oculus ii idis auct. scand., p. p. 



Cf. above p. 94. 



Probably derived from the plankton. 



Bare: Moskenstrommen r. Raftsund r. Gaukvsero r -f. 



Distribution: Arctic regions. 



C. horealis Bail. 

 Bail. Americ. Journ. Sc 1856, p. 3. A. Schm. Atlas, pi. Ii3, f. 11. 



Very rare: Raftsund, rr. Diameter 135 |i. Coarse structure; 

 areoles increasing towards the border, at the centre 3 Vs. near the 

 border 2 on 10 |i; the largesi ones only little larger than those at the 

 very margin. Large and very conspicuous ..papilla?" (poroides). 



