PLATE VI 



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Fig. 1. Coseinodit^ciis centndis Ehkb., Rattr. Valvc in side view, •'■'^"Vi. 

 „ 2. C. siihbidlu'n!< Jørg. n. sp. Sample from Evenstad (near Helsesrscii, Lofoten) II, ',':, ISO!), 0—200 m. \'alvc in side view, ^"'A. 

 .!. Thalastiiosira decipiens (Grun.), "^"/i- 



a. The Skjerstad Fiord V, -/i 1900. 0—420 m. The odd, asymmetrical, spine is distinctly seen (as also in the ti^'ures b— c). 

 The structure is very difticult to draw with a satisfactory result. There are some errors in the reproduction, especially 

 in the median part of the valve. When, however, the drawin.ffs ai'e compared with the description they will, I hope. 

 nevertheless be of some use. The lines are meant to show the dii-eetion of the rows of areoles; some of these are also 

 illustrated. 



b. The Herlo Fioi'd near Beriien, "A 189S. 



c. Folstad (the Ostnes Fiord, Lofoten), */i 1899, 0-3 m. Only tlie spines are shown in the liirurc. 



d. The Herlo Fiord. '■'/:• 189S. A valve in side view, showing the lony. somewhat curved, marginal spines and the hii:h 

 marginal zone. 



e. The Vest Fiord (Lofoten), ^% 1900, (I--25 m. A cell (frustule) in side view. The common foi-ms are L'enerally lowei 



f. O)tho!<ira avgidata Greg. Diat. of Clyde, pi. X, tigs. 43 and 43b, -""Vi- 

 ,, 4. Thalassiosira gravida Cl. A piece of a chain, "'''"/i. showing' the mucilaginous threads after stainiiiL;' with methylene blue. 

 „ 5. Th. hyaVma (Grcn.) Gkax. 



a— c. Valves of different specimens from Folstad, V4 1899, 0—3 m., ^'='"/,. The very fine structure is not illustrated, but 

 only the marginal spines, in b and c only that part of the valve Avhere the odd, asymmetrical, spine is found. In tin 

 figure a the more coarsely punctate median part is also shown. 

 d. Gaukværo, ^'/4 1899, — 3 m. A chain, """/i, showing the long mucilaginous threads of which only the outermost 

 illustrated. The central connecting band is a little too thick in this figure. 

 „ 6. Th. h-ijophda (Grun.). Cape Wankarema (North Eastern Siberia, Vega Expedition; slide in the Riksmusæum. Stockhdl 

 a, b. Valves of two different specimens, ''''■'"/ 1. Only a part of the border with marginal spines and the odd one are here sho^ 

 ,, 7. Pofosini gbiclaVis (Grun.). a, b, d from Stene in Bo (Vesteraalen), '"/4 1899. 



a. 2 cells, connected by a thick mucilaginous band, "7i. Outside this band two isolated connecting threads arc seen. 



b. 2 cells with protoplasma and chromatophores (conserved in formaline), '''"'1. 



c. A 3-jointed chain with very thick connecting bands, *=7i. A specimen from the Arctic Sea 1898. 



d. A 3-jointed chain. '^^"U, showing the long, diverging mucilaginous threads (after staining with methylene bluei. 



8. Eucampia grnenlandka Cl. Part of a chain. '■'■",. P.rettesnes (Lofoten), V* 1899. The transverse lines are much liner 1 1 

 represented in the figure. 



9. FragUaria njlindrm Grun. A valve of a small and short specimen, "'"'/i. Lille MoUa (near Raftsunti), •/4 1899. 



„ 10. F. idandiea Gbun. The Skjerstad Fiord V, -/, 1900. 0—400 m. A piece of a long chain after being ignited on co\ 



glass; "^"/,. Breadth 51 {jl; 16 — 18 striæ on 10 \i.. Connecting zone striate. 

 .. 11. Tltahissiotln-i.r nitzschioides Grun. IMie Skjerstad Fiord V, '74 1900, 0—420 ra. 



a. A zigzag chain of 4 individuals, •'^",1. 



b. 2 cells, one in side view, the other in valvar view. '■'7,. 52 ;«. long. 4 n broad; 11 pearls on 10 ;i. The undulation^ 

 the marL'in in the lower ligure are due to an error in reproduction. 



