565 





cells being very slightly siliceous. As a connection between the 

 cclls I found n very thin central thread like the threads in l'h. 

 hyalina (Grun.) Gran., and, consequently, I take the species to be 

 a Thalassiosira . in spile of the numerous connecting rings which 

 separate il from the other species; I think il heller to do so, rather 

 tlian create a new genus at a time when we do not know how 

 great a systematic valne this character has. (i ran. in his excel- 

 lent paper on Lauderia and Thalassiosira (Bemerk., 1900), mentions 

 that Cleve (Baff. Bay., 1896) has seen these numerous connecting 

 rings and that he evidently does not regard them to be a very valuahle 

 character, as he in his later papers always 

 calls it Coscinodiscus bioculatus. On the other 

 hånd Gran himself regards it as a character 

 of great value, and according to his definitions 

 of Ihe genera Lauderia, Detonula and Thalas- 

 siosira, the species in question ought to be a 

 Detonula; my reason for taking it to be a 

 Thalassiosira of a new section Coscinolauderia, 

 is because of its resemblance on the whole 

 to the other species, e. g. in its having one 

 row ofapicnli near the margin, in its central mucilaginous thread, etc. 



In one sample of September 1902 I found the auxospores 

 (Hg. 121) which are produced in the same manner as in T. grauida 

 (see Gran, Protophyta, PI. IV, figs. 57, 58). [See tables.] 



Grunow has found the species in samples from Cape Wan- 

 karema and the Kara Sea as well as in a sample from an ice-Hoe 

 from the west of Novaya-Zemlya, and Cleve has it from Davis 

 Strait. From these statements it should be an arctic form, but 1 

 think it is a boreal or temperate one belonging to the fjords 

 and is sometimes driven out in the ocean, as it is not seldom 

 found in the North Atlantic Ocean together with other diatoms, 

 but not in any great quantity. 



Fig. 121. Thalassiosira bioculata 



((■run. Ostf. o, chain; />, a cell 



devcloping into an auxospore; 



c, auxospore ( lv '/i). 



III. COSCINOSIRA Gran. 1900. 



7. C. polychorda Gran., Bemerk., 1900. p. 115. Coscinodiscus 

 polychordus Gran, Protophyta, 1897, p. 30, PI. II, lig. 33, PI. IV. lig. 56. 



A boreal, neritic species, which is rare around the Færoes; found 

 sparingly in March— April and single specimens also seen in September, 

 October, December and Mav. 



36* 



