Marine Plankton from the Kast-Greenland Sea. 269 



13. Coscinodiscus curvatulus Grun. var. karianus Cleve et Gru- 

 now, K. Svenska Vet. Akad. Handl., Bd. 17, No. 2, 1880, p. 113, pi. 7, fig. 

 129; C. curuatulus, var. geiuiina Grun., Diat. v. Franz Josefs Land, 

 1884, p. 31, ex parte, pi. D, fig. 13 (non fig. 14); C. ciirvalaliis Gran, 

 Nord. Plankton XIX, p. 35, ex parte, fig. 37 a. 



In two samples from the pack-ice, taken in July 1908, I found 

 rather sparingly a Coscinodiscus which agrees well with the form 

 quoted above, var. karianus of C. curuatulus, and to this form I also 

 refer the fig. 13 by Grunow's diatoms from Franz Josefs Land. It 

 has a single row of distinct apiculi. 



Gran has pointed out that probably several species are included 

 in Grunow's C. curuatulus. He gives figures of a form 

 from the Norwegian Sea which has no apiculi and in 

 which the low girdle consists of the two connecting 

 parts and a plain intercalary hoop. Our form has a 

 somewhat higher girdle in which each connecting Fig. 5. Coscino- 

 part has an intercalary hoop and the line between fj^'^^^ruu^van 

 the connecting part and the intercalary part is eleva- kariaims CI. & 

 ted and with a V-shaped curvature, see fig. 5. I think 

 that it is a distinct arctic species, but my material is too scanty to 

 decide the question. 



Distrib. (of var. kariaims): Arctic Sea, in paclc-ice; (of the main spe- 

 cies): widely distributed both in colder and warmer seas. 



14. Coscinodiscus Joergensenii nom. nov.; C. polijacanthus,\ai-. 

 intermedins Grunow, Diat. v. Franz Josefs Land, p. 29, pi. G, fig. 25; 

 Jørgensen, Bergens Museums Skrifter, 1905, p. 92; non C. intermedins 

 Ehrbg. 



In some samples from the pack-ice (July — August 1906 and 1908) 

 and from Danmarks Havn (October 1906, August 1907) I have found 

 rather scattered, specimens of a fasciculate Coscinodiscus of the sub- 

 tilis-group, which agrees well with Grunow's quoted description and 

 figure. As Jørgensen (1. c.) has suggested, it is distinct from the true 

 C. polijacanthus Grun. by having one row of small interfasciculate 

 apiculi and is closely related to C. curuatulus (at least to var. karianus) 

 from which it differs e. g. by a finer structure and straight fasciculi. 

 On the other hand it is allied to Thalassiosira bioculata from which it 

 is easily recognised by having only one (not two) central aréole and 

 by a less fine structure. I have not succeeded in finding out the 

 construction of the girdle exactly, but it has not the many inter- 

 calary connecting parts of Th. bioculata and the cells are not high. 



My figures Fig. 6 will show the structure of the valves and the 

 number of apiculi which is considerably lower than in C. polyacanthus. 



