12 P. T. CLEVE, HYDROGRAFISKA UNDERSÖKNINGAR. 



C. horealis Bail (Smiths. Contrib. 1854 p. 8, f. 22, 23 — 

 Brightwell M. J. IV, p. 107, Pl. VII, f. 12 to 15. C. hor. var, 

 BrlyhtwelUi Cl. Diat. of the Arctio Sea Pl. II, f . 7 — C. con- 

 volufum Castr. Challenger Diat. p. 78). — Filaments with 

 rather few cellules, strongly silicious. Foramina small, lan- 

 ceolate. Cellules in F. V. quadrate or rectangular, connected 

 by the basis of the setai, which originate inside the margin 

 of the valve; in S.V. broadly elliptical to orbicular, with 

 divergent setai. Setse of the lilament almost as strong as the 

 terminal, in horizontal direction. Terminal setse very diver- 

 gent. All setfe with a spiral of small aculei. — Breadth of 

 the filament 0,0 2 to 0,04 m. m. 



This widely distributed species is easily recognized by 

 its cylindrical, silicious cells, and the strong, aculeate setee, 

 arising from inside the margin of the valves. — Ch. boreale 

 Lauder (T. M. S. XII, p. 78, Pl. VIII, f. 7) is a distinct species 

 with isolated cells. 



C. compressus Lauder (T. M. S. XII, p. 78, Pl. VIII, 

 f. 6. — C. ciliatus Lauder 1. c. p. 77, f. 2; specimen with endo- 

 cysts? — Ch. sp. ScHtJTT. Ueber d. Gattung Chpet. Pl. III, 

 f. IV). — This species is remarkable for the setse of the fila- 

 ment, being partly delicate and partly strong and undulating. 

 If Ch. riliat. Lauder be this species, the figur e represents a 

 specimen with endocysts, which are described as having smooth 

 valves, surrounded by small bristles, arising from the margin. 



— Pl. II, fig. 3. 



C. rurvisetus Cl. (Kanonbaaden Haucks Togter p. 55, 1889). 



— This species is very characteristic and distinguislied by 

 its setse, curved in the same direction. The allied C. secundus 

 Cl., which has similar curved setee, is much coarser and its 

 terminal setae have a spiral of small puncta. This species 

 was found 1887 in May, June and August in the plankton of 

 the Danish Belts, at Hjselmen, Förnams, Aebleö, Fredericia and 

 Leesö. It occurred abundantly in November in plankton from 

 Gullmarsfjord. — Pl. I, fig. 5. 



C. ilanicus Cl. (Kanonbaaden Haucks Togter 1889 p. 55. 

 Diatoms of Finland p. 65, Pl. III, f. 18, 19. C. Wighami 

 V. Heurck Syn. Pl. LXXXII, f. 1. — Choet. sp. ind. Schutt 

 Ueber d. Gattung Chsetoc. Pl. III, f. 5). — Cells isolated or in 

 pairs, not forming filaments; in F. V. irregularly quadrate, 

 in S. V. almost orbicular with setéie, originating inside the 



