KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 153 



in 0,01 mm. at the ends), the 4 to 5 median striae being stronger and more radiate than the others, 

 which become transverse towards the ends. Connecting zone with numerous longitudinal divisions. 

 Frustules enclosed in mucous tubes of various shape. — ScJiizonema Grev. Ag. Consp. p. 18. W. Sm. 

 B. D. II p. 77 PL LVIII f. 364. Gbun. A. D. p. 42. V. H. Syn. p. 110 PI. XVI f. 2. Schizonema 

 sectio comoidea G-run. Bot. Centr. 1880. Schiz. comoides V. H. Syn. XVI f. 3. Schiz. apiculatum 

 and var. V. H. Syn. 1. c. f. 4—8. Navic. Delognei V. H. Syn. p. 110 PI. XI f. 13. 



Marine: Spitsbergen! Finmark! North Sea! Coasts of England (Sm.), Arctic America! Grreen- 

 land! Cape Deschneff (North Siberian Sea)! West Indies! Kerguelens Land! California! 



N. Grevillei is closely connected with N. rhombica, and it is questionable whether they 

 should not be imited. A great number of species of Schizonema have been founded on the shape 

 of the gelatinous tubes, in which the frustules are enclosed in the living state. As the frustules 

 of these forms are in all essential respects similar, there seems to be no sufficient reason for 

 adopting these species. 



38. N. Libellns Greg. (1857). — V. rhombic-lanceolate, convex, with acute ends. L. 0,0 6 5 

 to 0,1.5; B. 0,016 to 0,03 5 mm. Terminal nodules near the ends ; terminal fissures indistinct. Axial 

 and central areas indistinct. Strise 13 to 14 in 0,oi mm., on larger form, or about 18 inO,oi mm. 

 on smaller forms, very slightly radiate, almost parallel at the ends, distinctly punctate, puncta 

 (13 to 16 in 0,01 mm.) forming undulating, longitudinal rows. Connecting zone with numerous, 

 longitudinal divisions. — Greg. D. of CI. p. 528 PI. XIV f. 101. N. rhombica Donk. B. D. PI. IX f. 1. 



Marine: Scotland (Greg.), Macassar Straits! Oamaru, fossil! Sendai, Japan, fossil! 



N. Libellus is very similar to N. rhombica, but has the terminal nodules closer to the ends 

 and the striae almost parallel at the ends. The terminal fissures are difficult to observe as the 

 ends of the valve are curved downwards. 



39. N. (Libellus) complanata Grun. (1867). — V. linear-lanceolate, acute. L. 0,035; B. 

 0,005 mm. Striae 18 to 19 in 0,oi mm. Frustule rectangular. L. 0,054; B 0,033 mm. Connecting 

 zone with numerous, longitudinal divisions. — Amphora complanata Grun. Hedwigia VI p. 25. 



A. S. Atl. XXVI f. 45. Navic? compl. Grun. A. D. p. 42 (1880). 



Marine: Davis Strait! Sea of Kara (Grun.), Finmark! Bohuslan! Adriatic (Grun.). 

 Var. subinflata Grun. (1875). — Frustule rectangular. L. 0,04; B. 0,012 to O.ois mm. 

 Slightly inflated in the middle. — Amphora subinfl. Grun. A. S. Atl. XXVI f. 48, 49. 

 Marine: Adriatic (Grun.). 

 Var. hyperborea Grun. (1884). — Frustule rectangular. L. 0,0 5 ; 



B. 0,0165 mm. Striae 24 in 0,oi mm. — Amphora hyperborea Grun. 

 Franz Josephs Land D. p. 55 (3) PL I f. 10. 



Marine: Franz Josephs Land (Grun.), Sweden, Fiskebackskil! 



Nav. complanata is nearly akin to N. Libellus, bat is no Am- 

 phora, though the frustules have some resemblance to that genus. 

 The valves are rarely met with and difficult to observe. N. sub- 

 inflata and hyperborea are scarcely specifically distinct. 



The living frustule has two chromatophore-plates, each ex- 

 tending along the connecting zone from the ends towards the central 

 nodule. 



V 



40. N. (Libellus) HyalOSira Cl. (1822). — V. convex, thin, iV. complanata with cell-contents 

 lanceolate, rostrate or with rounded ends. L. 0,o25 to 0,03; B. 0,oo66 ^ *™''' magnified. 



mm. Striae 29 in 0,oi mm. punctate. Frustule slightly siliceous, quadrate. L. 0,025; B. 0,o 17 mm. 

 Connecting zone broad, with numerous and distant longitudinal divisions. — Cl. M. D. N:o 309. 

 Diatomiste I p. 77 PL XII f. 11. 



Marine: Firth of Tay! Cresswell (Deby Coll.)! 



K. Sv'. Vet. Altad. Handl. Bd 26, N;o 2. 20 



