172 KAARE MÜNSTER STRØM. 



apex rounded. Cell-wall thick and perforate, with great 

 and distinct perforations. The cell-wall is composed of 

 two distinct layers. Vertical view unknown, probably elliptic, 

 (ratio of axes about 2?). Size: long. 133,5 f^i, lat. 94,5 ,«, lat. 

 isthm. 36,7 /i. Pl, IV, Fig. 8. 



This is a very remarkable and distinct species, which can not 

 easily be confused with any other. It should be compared with 

 Gosmarium canaliculatum. W. & G. S. West, with which it agrees 

 in the perforations of the cell-wall, but it is very much greater, 

 and has also the double cell-wall. With C. scoticum W. & 

 G. S. West it agrees only in the size, the nature of the cell- 

 wall being different. It should also be compared with G. 

 pseudopachydermum Nordst. (Freshw. Algae New Zealand.). 

 I could not obtain the vertical view, but I measured the thick- 

 ness with the micrometer-screw (1/500 mm.) of the greatest 

 Zeiss-microscope (I b.) with regard to the breaking-index of the 

 medium. 



137. Gosmarium pyramidatum,. Breb. 

 Rare, only in a few samples. Size: long. 63 fx. 



138. Cosmariuin pseudopy ramidatum. Lund. 

 Frequent, and often in abundance. Size: long. 48,5 f«, 



lat, 29,5 jii, lat. isthm. 10 ^i. 



138 a. var. exornatum. (Printz) nob. 



Gosmarium exornatum. Printz: Ghloroph. Norwegen. 



I can see no reason for separating G. exornatum from C. 

 pseudopyramidatum as a species. Printz (I. c.) slates that 

 „the margins of semicells is convexer (dilatater) than those of 

 G. pseudopyramidatum", and that the apex is broadly rounded 

 with thicker membrane. — I have examined a great deal of 

 specimens of G. pseudopyramidatum, which agreed exactly with 

 Printz' figures, but had no central scrobiculations. The central 

 scrobiculations alone can not be regarded as sufficient to justify 

 a specific separation. 



