38 ASTRID CLEVE, ON RBCENT FRESHWATER DIATOM&. 



Melosira Ag. 



M. Roeseaiia Rabh. — V. H. LXXXIX, 1—3. 



Kv. 26, 32, Nu. 14, 17. 25, Km. 30. — Somewhat rare. 



M. distans KtJTZ. — V. H. LXXXVI, 21—27. 



Kv. 1, 26, 28, 34, Nu. 18, 37, Jm. 6, Na. 35, Gl. D. 45. 

 — Rather frequeut. 



M. creiuilata KtJTZ. var. ambi^iia Grun. — V. H. LXXXVIII, 

 12—15, A. S. CLXXXI, 12, 13. 



Kv. 9, 32, Nu. 2, 5, 17, Jm. 6, Ks. 15, 20, S.-K. 7, Ll. 21, 

 Km. 10, 30, Gl. D. 44 — Frequent. 



If we consider the distribution of genera and species in 

 the above list, we find tbat tlie following- genera are espe- 

 cially richly represented in Lule Lappmark, botb as regards 

 the number of species and the frequency of occurence: 



Pinnularia Ehb. 



Frustulia (Ag.) Rabh. 



CymheUa Ag. 



Gomplwtiema Ag. 



Eunoiia Ehb. 



Tahdlaria Ehb. 



On tbe other hand the following genera, of frequent oc- 

 curence in the freshwater flora of southern parts of Sweden, 

 and of other countries with a similar climate, are not (o), 

 or only sparingly, represented in Lule Lappmark. 

 Amphora Ehb. 

 o. Fleurosignia W. Sm. 



Cocconeis (Ehb.) Grun. 

 o. Bhoicosphema Grun. 



Surirclla Turpin. 

 o. CymatopJetira "VV. Sm. 

 o. Campylodiscus Ehb. 

 Epithemia Bréb. 

 Stephanodiscns (Ehb.) Grun. 



Several of the 270 forms 1 have hitherto found in Lule 

 Lappmark are thoroughly boreal or arctic. P. T. Cleve gives 

 a list of such arctic forms in Tbe diatoms of Finland p. 1), 



