ö ASTRID CLEVE, ON RECENT FRESHWATER DIATOMS. 



P. Spitsbergensis Cl Ms. 



Valve linear. O.055 to 0,o: mm. in length, 0,oo8 mm. in 

 breadth. Striae 15 in 0, 01 mm., parallel, interrupted in the 

 middle of the valve. Axial area one fonrth part of the breadth 

 of the valve. 



Jm. 6. — Rare. 



P. mesogon^yla Ehb. — A. S. XLV, 45, Cl. Finl. pl. I, 11. 



Kv. 32, Nii. 5, 17, 18, 25, 41, Jm. 6, V, 12, Tj. 42, S.-K. 22, 

 Gl. 47, Gl. D. 45. — Frequent. 



This species, occuring in northern parts of Finland (Cl. 

 Finl. p. 26) is pretty common also in Lnle Lappmark, and 

 may therefore be considered as a boreal form. 



P. stauroptera Grun. — V. H. VI, 7. 



Length of the valve 0,09 to 0, 15 mm. Striae 9, .5 to 10 in 

 0,01 mm., sometimes not interrupted in the middle of the valve. 



A craticular (sporangial?) form, like that figured in A. S. 

 XLIV, 31, occurs sparingly in V. 12. 



Ks. 15, Jm. 6, 31, V. 12, Tr. 38, Tj. 42, Gl. 43. — Mo- 

 derately frequent. 



Var. gibba Ehb. P. stauroptera var. parva V. H. VI, 6. 



Length of the valve 0,0.5 to 0,055 mm. Striae 11 to 11,5 

 in 0.01 mm. 



Kv. 1, 34, Jm. 6, S.-K. 33, Tr. 38, Tj. 42, Gl. 43. — 

 Moderately frequent. 



Var. capitata A. Cl. — A. S. XLIV, 33. P. dicephala 

 Ehb. var. stauroneiformis A. Schmidt 1. c. 



Valve with slightly undulating margins and subcapitate 

 ends, 0,05 to 0,o7 5 mm. in length, 0,oo8 to 0,oi mm. in breadth. 

 Striae 13 to 14 in 0, 01 mm., strongly divergent in the middle, 

 convergent in the ends of the valve; interrupted in the centre. 



Kv. 32, Km. 30, Jm. 6. — Somewhat rare. 



This form, evidently a variety of P. stauroptera, con- 

 nects that species with P. stomatophora Grun. (espeeially the 

 variety ornata A. Cl. (see below)). 



P. stomatophora Grun. — A. S. XLIV, 27, 28, 29. 



Jm. 6, Ks. 15, Kv. 9, Tj. 42, Gl. 47, Gl. D. 45. — Not rare. 

 Var. ornata A. Cl. n. var. — Pl. I, 3. 

 Valve 0,0 6 mm. in length, with slightly subcapitate ends. 

 Striae 14 in 0, 01 mm., strongly radiate, interrupted in the 



