BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 20. AFD. III. N:0 2. 13 



margin, in liorizontal direetion, sealn-ous with small, spirally 

 arranged aciilei. The setft* of tlie upper and lower valves are 

 divergent in an acute angle. — Cell-eontents coccochromatic. 



— Breadth of the valve O, o 2 m. m. 



This species is not to l)e confounded witli any other, being 

 one of the few not coneatenated species of Chootoceros. It 

 occurs in the Baltic in the Bay of Finland and around the 

 Danish islands. 



C. (lebUis Cl. N. Sp. — Filaments slightly silicious, thin, 

 multicellnlar, with rectangular foramina. Cellules in F. V. 

 rectangular or quadrate, not tonching each other; in S.V. 

 broadly elliptical, with the setse arising from the margin. 

 Setse of the filament very thin, ciirved in the same direetion. 

 Terminal seta? hardly stronger than the others. — Breadth 

 of the filament 0, 01 to 0,012 m.m. — Pl. I, fig. 2. 



This species may perhaps be the same as C. socialis Lauder, 

 but I am unable to identify them, having no specimen to 

 compare. It is one of the smallest and most delicate species 

 and so slightly silicious, that the cellules become altered by 

 exsiccation. The cell-contents are probably, judging from alko- 

 hol-preserved specimens. placochromatic. It resembles greatly 

 specimens of C. compressus, in which the coarse setse have 

 not been developed, but the latter species is coccochromatic 

 and has divergent setse. 



C. decipiens Cl. (Diat. of the Arctic Sea p. 11, Pl. I f. 5. 



— C. decipiens v. concreta Grun. Aret. Diat. p. 120). — Fila- 

 ments moderately silicious, multicellular, with rather narrow 

 foramina. Cells quadrate, with concave valves, touching each 

 other at the angles. Setaä of the filament rigid, coherent 

 at their basis, directed at a right angle to the axis of the 

 filament. Terminal setse somewhat coarser, moderately diver- 

 gent, finely transversely striate (strise 15 to 20in0,oi m.m.) 



— Breadth of the filament 0,0 2 6 m. m. 



This species, which was found rarely in November in 

 plankton from Gullmarsfjord, is recognised by its size, and 

 by the setse of the filament, being at their basis coherent for 

 a short distance, a characteristic not very well shewn in my 

 figure in the Diat. of the Arctic Sea. 



C. didymus Ehb. [Ber. lUb p. 75. M. Geol. XXXV, A. 

 17 f. 5. Brightwell M. J. IV, Pl. VII, f. 2 to 7. C. qastri- 



