BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 22. AFD. III. N:0 4. Ö 
Chetoceros septentrionalis ÖESTR. — Cellules isolated, slightly 
silicious, in sagittal view nearly quadrate, with concave val- 
vular margins. Angle prolonged in filiform, sagittal awns. 
Dimensions: long. ax. 0,006 to 0,014; sag. ax. 0,006 mm. En- 
docysts with similar, granulate valves, in sagittal view lenti- 
cular in transversal view elliptical. Dimensions: long. az. 
0,005; sag. ax. 0,01; transv. ax. 0,006 mm. — P1. II, 8. 
This form described and figured by Ozrstrur (Meddelelser 
om Grönland XVIII p. 457 Pl. VII f. 88) occurs abundantly 
in the plankton of the east Greenland. It is found sparingly 
in the plankton of Baffins Bay from the middle of August. 
It is very similar to, if not identical with C. pelagicus CL. 
(Diat. of the Arct. sea p. 11 PI I f. 4), but as this form 
occurs in chains, I cannot at present unite them. 
Chetoceros socialis LAUDER. —- Chains short, usually of 3 
to 6 cellules, slightly silieious. Foramina smaller than the 
cellules, narrow rectangular, scarcely narrowed in the middle. 
Cellules in sagittal view quadrate to rectangular, in trans- 
versal view elliptical. Valves slightly concave. Awns margi- 
nal, their basis very short, longitudinal, their prolongations 
delicate and filiform, the two arising from the one pole di- 
verging in an acute angle, the two from the opposite pole 
strongly diverging, almost transversal. Terminal awns not 
stronger than the others. Dimensions: long. ax. 0,006 to 0,012; 
sag. ax. 0,006 to-0,012; trarsv. ax. 0,002 to 0,004 mm. Endo- 
cysts unarmed enelosed in strongly silicious, cylindrical cellu- 
les, their valves somewhat dissimilar, one being more convex 
or conical than the other. Sag. ax. 0,005 mm. — Pl. II, 9. 
Being not quite sure about the identity of this form with 
LAUDER's species I have given the above description. The 
chains occur associated in a very strange manner by one of 
the awns being much longer than the others. These pro- 
longed awns are united at their ends, thus forming a myce- 
lium-like very intricate mass. 
The Chet. Wighami Grus. in Aret. D. Pl. VII f. 134 
doubtless represents the endocysts of this species, which thus 
occurs also in the sea of Kara. It occurs at the west-coast 
of Sweden in February. If the form of Baffins Bay really be 
identical with LAUDER's species, it occurs also at Hongkong. 
In Baffins Bay it is seen sparingly in May, but abundantly 
in September. 
