60 ARKIV rÖE BOTAXIK. BAXD l-t. NIO 9. 



Centricae. 

 Rhizosolenia (Ehb., Brightw.) Perag. 



Rhizosolenia Calcar avis Schültze. — Peragallo, Dia- 

 tomiste I, Tab. 16, f. 9. Nord. Plankt., p. 54, f. 66. 



Foss.: Sat. Panelia (Litorina-dep.). In samples from the 

 Geol. Commission of Finland. 



Distr, (mar.): Atlantic Ocean, spreading from its southern 

 parts. 



Rhizosolenia minima Lev. Medd. Soc. Fauna et Flora 

 fenn. 1904, p. 115, f. 7. A. S. Atl. Tab. 314, f. 1—7. 

 Bay of Viborg {feebly brack, iv.) (Levander). 



Rhizosolenia longiseta Zach. — Forschungsber. Plön I, 

 p. 38, f. 7. A. S. Atl. Tab. 314, f. 15—18. 



Spread in lakes from Nyland to S. Lapland (Levander). 

 Distr. (fresh iv.): Lakes of Scandinavia and Central Europe. 



Rhizosolenia longiseta Zach. var. Levanderi n. var. — 

 Rhizosolenia longiseta, »grosses bauchiges Exemplar», Levan- 

 der 1. c, p. 114, fig. 1. 



Kuusamo, Välijärvi. 



Distr. {fresh, w.): Sweden: Vänern, Alsen (A. Cleve-Euler). 



Rhizosolenia eriensis L. H. Smith var. europaea Hust. 

 A. S. Atl. Tab. 314, f. 24—26 (drawn from Finlandian speci- 

 mens). — Syn. Rhizosolenia eriensis Levander 1. c, f. 5, 6. 



Ks. Välijärvi, Tb. Keitele (Levander). 



The Rhizosolenia eriensis, stated by Levander to occur 

 in the two Finlandian lakes quoted above, is not typical, as 

 it has the connecting zone much more closely striate, with 

 8 — 10 costae in 10 \i. Original specimens of Rhiz. eriensis 

 from Lake Erie, as well as the same species from Vänern, 

 Sweden, have only 4 — 5 costae in 10 a. The Finlandian form 

 thus ought to be distinguished as a new variety, as Hustedt 

 has done, with the remark, however, that this variety comes 

 very near to Rhizosolenia eriensis var. morsa West. Maybe 

 both varieties are identical. 



