564 



Fig. 119. Thalassiosira subtilis ( Ostf.) 

 Gran. An aggregation of cells em- 

 bedded in the mucilage i 15 "/V. and 

 a valve of a cell showing the »pseu- 

 do-nodule« («o/ t ). 



each valve are distinguishable. 



ferent cells afler their position in the mucilage; that is at least the case 

 judging Ironi preserved material. In some of the cells two daughter- 

 cells are formed; they are somewhat separated from each other and 



yet kept together by the connecting zone. 

 After ignification and embedding in styrax 

 the structure of the cell is seen with diffi- 

 culty; the valve (16 — 32 \i in diameter) is 

 arched and without any visible structure; 

 seen from the front, a small, but distincl 

 »pseudo-nodule« is to be observed at some 

 distance from the margin, which appears 

 to be very faintly and closely spiniferous, 

 but the last observation may be wrong. 

 In girdle-view a connecting band and two 

 narrow connecting rings, one belonging to 

 The cells are thus formed much in 

 the same way as in the Thalassiosirae of the section Pseudolauderia, 

 and by the absence of the mucilaginous thread and the existence 

 of the amorphous mucilage this species seems to form a connecting 

 link between this section of the Thalassiosira and the Landeria, 

 especially L. glacialis (Grim.) Gran. 



It has been found once (March 1900) around the Færoes. 



6. T. bioculata (Grun.) Ostf. n. nora. ; Coscinodiscus bioculatus Gru- 

 now, Diat. Franz Josefs Land, Denkschr. d. K. Akad. d. Wissensch., 

 Bd. 48. Wien 1884, p. 107, PI. C, fig. 30, & D, figs. 1-2; Gleve, Baff. 

 Bay. 1896, p. 10, PI. II, fig. 13; Coscinodiscus 

 sp. Ostenfeld, Iagttagelser, 1900, p. 52. 



A chain- diatom predominates in the 

 samples of August — September of 1902; the 

 same species occurs also in April — May, but 

 rarely. The cells are cylindrical, often higher 

 than they are broad (diameter 30 — 60 /«, 

 height 40 — 60 ,»). Besides the connecting band 

 a great number of connecting rings occur, 

 commonly 4 or 5 on each theka. It is without 

 doubl identical with Coscinodiscus bioculatus 

 of Grunow, the structure of the valves being exactly like that of 

 his ligures. Markings are fasciculate, punctiform; central space has 

 two round granules; apiculi very small, close lo the border and in 

 one row; bul the structure is diflicult to dislinguish owing to the 



Fig. 120. Tlialassiosira bioculata 

 (Grun.) Ostf., ditl'erent cells show- 

 ing the connecting rings. ('1 cells 

 to the lefl ■•""■'i, cell to the right«« ,. | 



