A. CLEVE-EÜLER, DIÄT. FLORA OF FINLAND. 65 



living pelagic Hyalodiscns stelUger in the Skagerak. The latter 

 is only about 50 \i. in diameter. The figure in van Heurck's 

 Synopsis represents an intermediate form, 70 [j. in diameter. 



Cyclotella Kixz. 



Cyclotella comta Ehb. var. oligactis (Ehb.) Grun. — 

 V. H. Syn. Tab. 93 f. 18. 



Foss. : Kk. Knjäsba, rare. 

 Distr. {fresh w.): Lara. 



Cyclotella comta Ehb. var. spectabilis n. var. — PI. 3, 

 f. 68. — SynJ Cyclotella halatonis Pant. v. hinotata Pant. 

 Balat., p. 105, Tab. 15, f. 331. 



Valve 30 ;j. in diameter. Marginal striate zone about one 

 third of the radius; marginal puncta (pores) alternating with 

 2 or 3 striae. Five distinct channels. Centrum of the disc 

 covered with radiating rows of puncta, leaving a ver}^ small 

 blank annulus round two central puncta. 



Foss.: Ab. Hindersmossen, in the undermost (eldest) 

 strata from the Ancylus-e'poch, where also are found some 

 diatoms of brackish water. 



This large and beautiful form makes a remarkable tran- 

 sition between Cyclotella comta var. radiosa and Cycl. hodanica. 



With the former it has the rather narrow, striate zone 

 and the fine striae of equal length in common, with the latter 

 the five distinct channels and the large size. Moreover, the 

 disposition of the marginal puncta is strictly intermediate, as 

 these puncta alternate with two striae in Cyclotella hodanica, 

 but with three striae in Cyclotella comta var. radiosa; cfr A. 

 Cleve-Euler, Cycl. bod , p. 441. — Most probably the quoted 

 variety of Cyclotella halatonis Pant. (= C. comta Ehb.) is 

 identical with the present form. — Another related form is 

 Cycl. comta var. af finis Grun. (V. H. Tab. 93, f. 11 — 13), 

 without visible channels. 



Cyclotella bodanica Eulenst. — V. H. Syn. Tab. 93, 

 f. 10. A. Cleve-Euler, Cycl. bod., p. 441, f. 2 a, b. 



Foss.: Kk. Knjäsha, rare. 



Distr. (fresh u\): Spread in the larger and colder lakes 

 of Europe, as alpine lakes, lakes Vänern and Vättern in 

 Sweden. 



Ark-iv för botanik. Band 14. X.o 9. 5 



