BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 22. AFD. III. N:0 4. 5 
along the east-coast of Greenland. I will, in the following, 
treat first of the forms, which constitute the plankton, and 
later on of the last named diatoms, which after all may pro- 
bably be derived from molten ice-flakes. 
Plankton-diatoms. 
Achnanthes taeniata GRUN., formerly met with in the sea 
of Kara, occurs sparingly in the August-plankton. 
Amphiprora (paludosa var.) hyperborea GRUN. is a true plank- 
ton-diatom, occurring in long, sometimes sligthly spirally 
twisted, bands, formed by the frustules firmly coherent by 
their keels. It occurs by no means sparingly in the May- 
plankton from Disco, but not in the other samples. It has 
been found in the sea of Kara. 
Asteromphalus atlanticus CL. N. sp. I have formerly !) con- 
sidered this diatom as a variety of A. Brooket, later?) as a 
form of A. Hookeri, but am now more inclined to believe it 
to be a distinct species, peculiar to the Atlantic and per- 
haps also the Mediterranean. It is smaller and has a less 
number of rays than ÅA. Brooker, figured by GREVILLE and in 
A. ScHmiors Atlas (P1. XXXVIII, 21 to 23), but agrees better 
with the small form from Campeachy Bay (Atlas 1. c. f. 9), 
also with A. robustus PEraG. (D. de Villefranche PI. II f. 15). 
Description: Disc orbicular, 0,03 to 0,04 in diameter. 
Segments 6 to 7, inside truncate, puncta forming rows pa- 
rallel with the margin and oblique rows, both 12 in 0,01 mm. 
Radius of the bhyaline area about half of the radius of the 
dise. Centro-lateral area clavate, reaching a little beyond 
the centre of the valve, and sending off, partly from the 
sides, partly from the top, umbilical lines, which are un- 
branched and either nearly straight or angularly bent in 
the middle. 
Asteromphalus is a genus belonging to the plankton of 
the warmer seas. ÅA. atlanticus has hitherto not been found 
at Spitsbergen, Finmark or in the North-siberian sea, for 
which reason it seems not to belong to the polar seas pro- 
perly. On the other hand it has been found in soundings 
1) Diatoms of the arctic sea p. 10 P1. IV f. 19. 
2) Diatoms of Vega p. 487. 
