Marine Plankton from the East-Greenland Sea. 265 



Hyalodiscus Ehrbg., 1845. 

 9. Hyalodiscus laevis b^hrbg., Monatsber. Berlin. Akad. Wis- 

 sensch. 1845, p. 78; Cleve u. Grunow, K. Svenska Vet. Akad. Handl., 

 Bd. 17, No. 2, 1880, p. 110; Peragallo, Diatom marin, de France, pL 119, 

 fig. 20; H. siibtilis Bailey, Smithson. Contrib. to knowledge, vol. 7, 1854, 

 p. 10, fig. 12; W. Hendry, Quart. Journ. Microsc. sc, 1861, p. 179; 

 Cleve u. Grunow, 1. с ; Gran, Bibliotheca botanica, Heft 42, p. 5, pi. 1, 

 fig. 19: Peragallo, 1. c, pi. 119, fig. 7. Cfr. Stockmayer, Annal, к. к. 

 naturh. Hofmuseum, Wien, XXIII, 1909, p. 69. 



In some samples from Danmarks Havn I found sparingly a large 

 species {150 -\-ll fj. in diameter of the valve) of Hyalodiscus which, 

 I think, is identical with Grans H. siibtilis from Karajak Fjord. On 

 the other hand I cannot find any difference of valve between H. 

 lœvis Ehrbg. and Я. siibtilis Bail. Already Hendy (I.e.) has suggested 

 that the distinctive marks in the proportion between the entire valve 

 and the central part (umbilicus) as well as in the structure of the 

 "umbî7/cus" arc value-less, and my here given figures (Fig. 1) which 



Fig 1. Hyalodiscus laevis Ehrbg. 250 t. m. 



are chosen as extremes will, taken together with the figures bv 

 Peragallo, show that these characters are subject to great variabi- 

 lity. Therefore, I find it necessarj' to unite the two species in one 

 to which H. scoticus (^Kutz.) Grun. must be referred as a dwarfy 

 variety. — July — September. 



D i strib. Coast-species, not true plankton form, found scattered over 

 the earth, especially in colder regions; often found in fossil depots. 



Cosciiiodiscus Ehrbg., 1838. 



10. Coscinodiscus centralis Ehrbg., Abhandl. Berl. Akad., 1838, 

 p. 129; Mikrogeologie, i)l. 18, fig. 39. pi. 22, fig. 1 ; Jørgensen, Bergens 

 Museums Skrifter, 1905, p. 93, pi. 6, fig. 1; Gran, Nord. Plankton XIX, 



