L98 



E. Joreeusen. 



the whole doubtful, whether these two species always can be 

 distinguished from each other. 



A more essential difference than in the structure of the valve 

 is found in the form of the cell (frustule). A. crassus has high 

 cells, usually higher than broad, with thick walls, also in the con- 

 necting /one: here there is also a conspicuous difference in width 

 between the two valves. A. Ehrenbergii, however, forms low cells, 

 broader -- often much so — than high, and the two valves have 

 nearly the same diameter. 



The valve of A crassus is flat from the centre to some di- 

 stance from the border, where there is a high and steep marginal 

 zone. 



Somewhat rare: Stamsund r, Raftsund r. Gaukvsero r, Stene r. 

 Occurs also in the plankton samples. 



Distribution: Western Europe. After all, it is most probably 

 identical with Ewpodiseus crassus W. Sm. (Cf. Van Heurck 1. c. 

 and Traite d. Diat. p. 524). 



Note. In the sample from Stene, several broken valves with 

 a rather large disc occurred, somewhat similar to Xanthiopyxis? 

 umbonata Geev., cf. Van Heurck Traite d. Diat. p. 512, fig. 263, 

 which cannot, however, be referred to the genus Xanthiopyxis 

 Eheb., a doubtful genus including what are probably resting spores 

 of Chaetoceros (cf. Schutt. in Exgler and Prantl.. Natiirl. Pflan- 

 zenfamil, Theil I, Abth. 1 b, p. 148). Structure rather fine, similar 

 to that of Coscinodiscus ; valve rather convex, with numerous large, 

 slender, conical spines, as in the figure referred to. Undoubtedly 

 a fossil species. 



2. Melosirese. 

 Ooseinosira polychorda (Gear) Gran. 



Cf. above p. 97. 



Derived from the plankton. 



Very rare: Stamsund r. GaukvaTo r. 



Distribution: Cf. above p. 97. As stated before (p. 196) 

 this species seems also to occur singly, and is then easily mistaken 

 for Coscinodiscus lineatus. At any rate, forms occur in which the 

 peculiar transverse processus at the semiradius are wanting. 



Tlialassiosira Cl. 

 T. gravida Cl. 



Cf. above p. 96. 



In bottom samples the strong resting spores (endocysts) of this 

 species occur, though seldom (much more so than would probably 

 be the case, if this species generally „oversummers" on the bottom). 



Rare: Stamsund r +• Svolvser r. 



Distribution: Cf. above p. 96. 



T. decipiens (Grun.) J< 



('('. above p. 96. 



Undoubtedly derived from the plankton. 

 Hare: Stamsund r, Svolvser r, Gaukvaero r +. 

 Distribution (of Coscinodiscus decipiens Grun.): Caspian Sea. 

 Great Britain and Ireland. West coast of Norway. 



lI«>lo*ira Ag. 



M. granulata (Eheb). Ralfs. 



Van Heurck Synopsis p. 200, pi. 87, figs. 10—12. 



Fresh water species. 

 Very rare: Gaukvaero, rr. 



Distribution : Frequent in fresh water, especially in Western 

 Europe. Franz Josefs Land. 



M. Roeseana Rabenh. 



Van Heurck Synopsis p. 199, pi. 89, figs. 1 — li. 



Fresh water species. 



Very rare: Ostnesfjord, rr. 



Distribution: Common fresh water species. Greenland l Ostrup). 



3/. Borreri Grev. 

 Grew in Hook. Brit. Fl. II, p. 401. Van Heurck Synops. p. 198, pi. 85, 



Bgs. 5—8. 



Very rare: Svolvser, rr (var. ad hispid. Castr.). 

 Distribution: Frequent on the coasts of Europe. Green- 

 land (Cl.). 



Paralia sulcata (Ehrb.) Cl. 

 Cleve Diat. Avct. Sea 1873, p. 7. GoMionella sulcata Ehrb., Mikrogeologie 



pi. 18, 1. 



Common: Moskenstrommen -f-, Stamsund e, Svolvser c, Raft- 

 sund r -f-, Brettesnes — Skroven r, Ostnesfjord e, Gaukvser0 cc, 

 Stene c. 



Distributim : Frequent on the coasts of Europe and America. 

 Arctic regions. 



forma coronata (Ehrb.) Grun. 

 Van Heurck Synopsis pi. 91, f. 18. OaUioneUa coronata Ehrb., Mikrogeologie 



pi. 38, xxn. fig. 5. 

 Rare: Svolvser r, Stene r. 



Cyolrttella Kutz. 



C. striata (Kutz.) Grun. 



Grun. in Cleve ft Grunow Arct. Diat. 1880, p. 119. Van Heurck Synopsis 



p. 213, pi. 92. figs. 6—10. Coscinodiscus striata* Kutz. 



Rare: Stamsund r, Raftsund r, Stene r. 

 Distribution: Frequent in brackish water. Western Europe. 

 Baltic Sea. Warmer parts of Asia and Africa. 



C. eomta (Eheb.) Kutz. 

 Kutz. Spec. Algar. p. 21. Van Heurck Synops. p. 214, pi. 92, figs, lfi — 22. 



Fresh water species. 

 Very rare: Gaukvsero, rr. 

 Distribution: Western Europe. 



llvaloriix-us Ehrb. 



H. seoticus (Kutz.) Grun. 



Grun. in Journ. Royal Micv. Soc. 1879. p. 690, pi. 21, f. 5. Van Heurck Synops. 



pi. 84, figs. 15—18. Cyelotella s. Kutz. Baoill. p. 50, pi. 1, figs. II, III. 



Frequent: Stamsund r, Svolvser +. Gaukvsero -4- c, Stene r +. 

 Distribution: Western Europe. Bosporus. Arctic regions. 



