E. Joi-gensen. 



the whole doubtful, whether these two species always eau he 

 distinguished from each other. 



A more esseutial difference than in the structure of the valve 

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

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

 necting zone; 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. cmssiis is flat from tlie centre to some di- 

 stance from the bordei', whei'e there is a high and steep marginal 

 zone. 



Somewhat rare : S tamsund r, Raftsund r, Gaukværo r. Stene r. 

 Occurs also in the plankton samples. 



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

 identical with Eupodifiens cynsxus W. Sm. (Cf. Van Heukck 1. c. 

 and Traité d. Diat. p. 524). 



Melosira Ag. 



M. (jranulata (Eheb). Ralfs. 



Van Hel'RCK Synopsis p. 200, pi. 87, figs. 10—12. 



Fresh water species. 

 Vei-y rare: Gaukværø, rr. 



Dlstiihution : Frequent in fresh water, especially in Western 

 Europe. Franz Josefs Land. 



21. Boescana Rabenh. 



Van Heørck Synopsis p. 19(1, pi. 89, figs. 1—6. 



Fresh water species. 



Very rare: Ostnesfjord. rr. 



Distrihution: Common fresh water species. Greenland (Ostrup). 



M. Borreri Grev. 

 Grev. iu Hook. Brit. Fl. II, p. 401. Van Hel-rck Synops, p. 198, pi. 85, 



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

 a rather large disc occurred, somewhat similar to X(mthiopyxi><'^ 

 umbonata Gkev., cf. Van Heøeck Traité d. Diat. p. 512, fig. 263, 

 which cannot, however, be referred to the genus Xanthioju/xiK 

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

 of Chætoceros (cf. ScHiiTT. in Engler and Pkantl., Natiirl. Pflan- 

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

 to that of Co-seinodiscm ; valve rather convex, with numerous large, 

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

 a fossil species. 



2. Melosireæ. 



Cosciiio.«iil'a polycborda (Gran) Gran. 



Cf. above p. 97. 



Derived from the plankton. 



Very rare: Stamsund r, Gaukværø r. 



Dislnhiiiwn: Cf. above p. 97. As stated before (p. 19G) 

 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. 



TlialasMiosira Ci.. 

 T. gravida Cr,. 



Cf. above p. 96. 



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

 species occur, thougii seldom (much more so tli;\n would ])robably 

 be the case, if this species generally „oversummcis'' on tiio bottom). 



Rai'e: Stamsund r +, Svolvær r. 



Disfrihatwn: Cf. above ]>. 96. 



T. decipicns ((i 



:.) J. 



Cf. above p. 96. 



Undoubtedly derived from tiio plankton. 

 Rare: Stamsund i-, Svolv;er r, Gaukværø i' +. 

 Distrihution (of Coscinodiscus decipiens Geun.): Caspian Soa. 

 Great liiritain and Ireland. West coast of Norwav. 



Very rare: Svolvær, rr (/vo-. ad hi.^^pld. Castr.). 

 Distrihution: Frequent on the coasts of Europe. Green- 

 land (Cl.). 



Paralia sulcata (Ehrb.) Cl. 

 Cleve Diat. Arct. Sea 1873, p. 7. Gallionella sulcata Ehrb., Jlikrogeologie 

 pi. 18, 1. 



Common: Moskenstrommen -f, Stamsund c, Svolvær c. Raft- 

 sund r +, Brcttesnes— Skroven r, Ostnesf^jord c, Gaukværø ce. 

 Stene c. 



Distribution.: Frequent on the coasts of Europe and America. 

 Arctic regions. 



forma coroaata (Ehrb.) Grun. 



Van Heurck Synopsis pi. 91, f. 18. Gallionella coronata Ehrb., JIikrogeol..i;i,. 



pi. 38, XXII, fig. .5. 



Rare: Svolvær r. Stone r. 



C.vclotolla KiJTz. 



C. striata (Kltz.) Grcn. 



Grun. in. Cleve et Gri-now Arct. Diat. 1880, p. 119. Van Hel-rck Synapsis 



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



Rare: Stamsund r, Raftsund r, Stene r. 

 Distribution: Frequent in brackish water. Western Eurojie. 

 Baltic Sea. Warmer parts of Asia and Africa. 



C. couita (Ehrb.) Kl-tz. 

 KiJTZ. Spec. Algar. p. 21. Van Heurck Synops, p. 214, pi. 92. figs. 16—22. 



Fresh water species. 

 Very rare: Gaukværo. rr. 



Distribution: Weslcni iMiropc 



ll.>al4>diKciiN Kiiiiii. 



U. scoticus (IvcTz.) Grun. 



Grun. in Journ. Royal Micr. Soc. 1879, p. 690, pi. 21, f. n. Van Heurck Syn..]!-. 



pl. 84, figs. 1.5—18. Ci/clotella s. Kutz. BaciU. p. .50, pi. I, figs. H, III. 



Frequent: Stamsund r, Svolvær -f, Gaukværø + c, Stener +. 

 Distribution: Western Europe. 13o.sporus. Arctic regions. 



