E. Jørge 



rar. ventricosa (Gbeg.) Cl. 

 Cl. 1. e. p. 13.1. Amphora v. Greg. Diat. of Clyde p. .511. pl. XII. f. «8. 



Not unfrequent, Mosken.strømraen r. Stam.sund r, the Ø,stnes- 

 fiord r -{-. Stene r, Gaukværø +. 



_ Answers completely to Gregory's species, but is very variable. 

 Distribution: Coasts of the North Sea. Sweden. Arctic 

 regions. The Mediterranean. Red Sea. 



Epitheniia Bréb. 



U. turgida (Eheb.) Kutz. 



Kdtz. Bacill., pi. 5, f. 14. Vax Hei'Rck Svnops.. pi. 31, 



1—2. Navicula 



f. Ehrb. 18.30. 



Fresh -iwater species 



var. Westerinaani (Ehrb.) Grun. 



Grun. in Wien Verb. 186:^, p. 32.5. Van Heurck Svnops. p. 138, pi. 31, f. 8. 



Naviada W. Ehrb. 1833. 



Very rare: Gaukværø, r; Moskenstrømmen, r. 

 Distribution: In brackish water. Coasts of the North Sea. 



E. avfjiis (Ehkb.) Kutz. 



KiJTZ. Bac-ill. pi. 29, f. 55. Vak Hehkok Synops, pl. 31, figs. 15 — 17. Eunotia 



argits Ehrb., Mikrogeol. pi. XV A, f. 59. 



Very rare: Brettesnes — Skroven r, Gaukværø r. 



Distrihiition: Fresh water species; also in brackish water. 



Frequent, especially in Northern Europe and in alpine localities. 



E. zebra (Ehrb.) KtJTz. 



KtJTz. Bacill. pi. 5, f. 12; pi. 30, f. 5. Van Heurck Synops, pl. 31, figs. 9, 

 11 — 14. Eunotia z. Ehrb. Inf. p. 191, pi. 21, f. 19. 

 Very rai'e: Gaukværø r, Stene r. 

 Distribtitioii: Common fresh water species. 



E. tnusculus KiJTz. 

 f. <i. Van Heitrck Synu 



32, tlKS. 14— Ir 



rar. constricta (Bréb.) V. H. 



Van Hei-hck Synops. ]). 140: Ti-aité d. Diat. p. 297. pi. 9, f. 3liO. EpWiemiac. 



Bréb. in W. Sm. Brit. Diat. 1. p. 14, pi. m, f. 248. 



Very rare: Svolvær r, Gaukvæio r. 



Distribution: Coasts of the North Sea and Western Europe. 

 The Mediterranean. 



KtJTZ. Bacill., pi. 



Rare: Svolvær, r. 



E. gibberula Kutz. 

 t. Van Heurck Ti-aité d. Diat., p. 297, pi. 30, f. 825. 



rar. prodiicta (inuN. 

 Van Heurck Synops, pl. .32, figs 



-13. 



Rare: Stamsund, r. 



Distribution: Marine, also in lirackisli and fresh water (rar. 

 producta Grun.I. fi'equent in h^uropc and .\iiieiica. 



RhopulodJH (jibbu (Eniiii.) Otto Mull. 1895. 



Epithcniia tjUiha Kutz. IJacill. p. 35. pi. 4, f. 22. Van Heurck Synops, p. 1.39i 



pi. 32. figs. I- -2. 



rar. ventricosa (KiiTZ.) Grun. 

 Grun. in Wien Veiii. 18(i2, p. 327. E2)itJiemia ventricosa Kutz. Bacill. pi. 30, f. 9. 



Very rare: Gaukværø, r; the Østnesfiord, r. 

 Distribution: Common fi-esh water species. 



G-eneral lemarks on the cliaracter of the bottom diatom flora. 



The most striking facts regarding the distribution of the dia- 

 toms in the foregoing list of bottom species are, that the arctic 

 forms are rare and that the floi'a, on the whole, has a much more 

 pronounced southern character than would be expected from the 

 geographical situation. This is in sharp contradistinction to the 

 character of the diatom flora during ,,the diatom inflow" of plankton 

 species in spring (cf. above p. 88), when the actual arctic species 

 predominate. 



Generally speaking, the bottom flora shows a remarkable 

 agreement with that of the east coast of Scotland. It is especially 

 striking that a great many of the species described by Gregory in 

 Diatoms of the Clyde (1854) are common to these two regions, 

 situated at a rather considerable distance from each other. On the 

 other hand, these species also occur on the west coast of Norway, 

 at any rate most of them. It may, consequently, be concluded that 

 the characteristic western bottom flora of diatoms wliich inhabit 

 the coasts of the North Sea extend to the north as far as to past 

 the Vest-Fioi'd, probably, however, but little farther. 



For the sake of clearnes.s, I divide the species found into (; 

 gr-ou])S: 

 I. The actual arctic species, only found in the ai'ctic r'egion. 

 11. Species with a western and arctic distribution. 



III. Species with a very wide disti'ibution, occurTing trom southern 

 i-egions right up into the arctic one. Some of these species 

 seem to be cosmopolitan. In I]ui'ope, the species belonging 

 to this gi'oup are generally found fr-om the Mediterr'anean to 

 the ai-ctic regions. 



IV. Western species, especially known •from tire coasts of the Noi'tli 

 Sea, but not befor'e mentioned from the arctic zone. 



V. Species with a southei-n and we.ster-n distr-ibution. generally 

 occurring fr-om the Mediterranean — or- still farther to the 

 south — to the coasts of the Norih Sea. 

 VI. Species with only southern distribution, not before found so 

 far north as on the coasts of the North Sea. 



Most of the species observed belong to group III, and man\ 

 of these species will probably later orr be found to have a still widn- 

 distribution than is at pi'esent known. For such more oi' 1c>n 

 decidedly cosmopolitan species, a thorough treatise on their varieties 

 and forms is a very important and valuable work, indispensable 

 when one wishes to obtain an accur-ate knowledge of the distr-ibution 

 of identical and closely related species. Notwithstanding the exten- 

 sive matci-ial consisting of an immense number of facts and obser- 

 vations, often made with the utmost care and accur-acy as to details 

 in structure, we are still obliged to acknowledge with r-egret that 

 our- krrowledge of the individual vai-iations and r-eal constancy ni' 

 the var-ious distinguishing characters is ver-y deficient. 



These species play an nnimportant jiart with regai-d to the 

 char-acter of the flora. It is. hewevei-, an interesting fact that, 

 appar-errtly, so many sjrecics of diatoms ar-e common to most seas 

 of the world. Even if a good many of these widely distr-ibuted 

 species, on a moi-e thoi-ough examination, should prove to consist of 

 similar-, but separate species, having ditter-ent areas of distribution, 

 there will still i-emain a great number of species which, in Europe. 

 occur fr-om the Mediterr-anean to the Arctic Sea. It must, however-, 

 be i-emembered that the valves of diatoms ai-e almost of eternal 



