BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 1. N:0 13. 7 



radiating and curved lines, crossing each other. F. V. quad- 

 ratic; with tnmcate angles connecting membrane broadly 

 linear, without any distinct sculpture. Frustules in tlie livmg 

 State connected by means of a central fine thread of mucus 

 into long filaments. The form of the cells agrees with 

 Coscinodiscus, but the sculpture is much more fine, than in any 

 known species of that genus. The row of submarginal spines 

 approximatcs it to Cresswellia, but the spines of different frus- 

 tules do not touch each other. The doubtful genus Syste- 

 phania niay be the same a Thalassiosira. 



Thalassiosira Nordenskiöldii Cl. N. Sp. Scarcely siliceous, 

 sculpture of the fullgrown frustule minutely punctate visible 

 only on dry specimens and by careful ^illumination. Colour 

 of the dry valve påle yellowish brown. 



Diam. 0,0 17—0,035 m.m; Height. (F.V.) 0,oi— 0,02 m.ra. 



The cellules are arranged nearly in the same manner as 

 on Hyalodiscus stelliger, but they are much smaller. The frus- 

 tules are connected in the same manner as those of Tricera- 

 tium undulatum BrigUw. In S. V. the species resembles 

 Systephania Aiiglica OONKIN. (M. J. n. s. I pag. 12 Pl. I 

 fio-. 14) but I am not able to identify it with that species, 

 which has not been completely described. 



The Thalassiosira Nordenskiöldii occurs in enormous large 

 masses, floating on the surfacc of the sea and colouring it for 

 many miles in extent. Sometimes no other diatom is found 

 among it. JDavis Strait Lat. 62° 36' Long. 52° 50'; Lat. 63° 

 30' Long. 52° 40'; Lat. 61° 25' Long. 50° 50'. (Th. M. Fries) 

 Pl. I fig. 1 a & b F. V. c & d S. V. 



12. Paralia sulcata (Ehb) Cl (Galionclla sulcata Bhb. 

 M. G. e. g. T. XVIII lig. 1. Melosira sulcata Kö Bac. pag- 

 55 T. II fig. 7. Orthosira marina Sm Syn. II pag. 59 Pl. LIII 

 fig. 338. Paralia marina Heib. Consp. Crit I). Dan. pag. 33). 

 Spetsbergen; Beeren Eiland, Finmarken Grötsund, Davis strait. 



The species occurs in all seas. 



13. Melosira mimmuloides (Lyngb) Kg (var. y Sm Syn 

 II pao-. 55). Spetsbergen Hackluyts. Greenland somewhat rare. 



?14. Actinooyclus Ehrenbergii Ealfs (in Prit. Inf. pag. 834 

 1861). Spetsbergen Kings Bay (160 fath) but observed nowhere 



