KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 89 



54. p. Flamma A. S. (1876). — V. linear, with broadly rounded ends. L. 0,i4 to 0,i5; 

 B. 0,025 to 0,02 mm. Axial area very narrow, central orbicular. Striaj subparaUel, flexuose, in 

 the middle radiate, 7 to 9 in 0,oi mm., crossed by a broad band. — Nav. Flamma A. S. Atl. 

 XLII f. 27, 28. 



Fresh water: Demerara River! 



55. P. Flammnla A. S. (1876). — V. linear, with somewhat dilated and capitate ends. 

 L. 0,1 ; B. 0,015 mm. Axial area narrow, central orbicular. Striae radiate, 9 in 0,oi mm. — Nav. 

 Flammula A. S. Atl. XLII f. 26. 



Fresh water: Demerara River! 



Seems to be only a smaller form of the preceding. 



56. P. oregonica Cl. N. Sp. — V. linear, slightly triundulate, with cuneate, subacute ends. 

 L. 0,113; B. 0,015 mm. Median line filiform with approximate median pores, and semicircular 

 terminal fissures. Axial area very narrow, widened in the middle to a rhomboid-lanceolate central 

 area. Striae 11 in 0,oi mm. divergent in the middle, convergent at the ends. — A. S. Atl. XLIII f. 34. 



Fresh water: Oregon, fossil! 



57. P. major KtiTZ (1833). — V. slender, linear, gibbous in the middle, and at the rounded 

 ends. L. 0,2 to 0,3; B. 0,03 mm. Median line not complex, oblique; terminal fissures comma- 

 shaped. Area linear somewhat less than a third of the breadth of the valve, scarcely widened in 

 the middle, convergent at the ends, crossed by a narrow band. — Frusiulia major KtJTZ Syn. p. 19 

 f. 25? Nav. maj. Kutz Bac. p. 97 PL IV f. 19, 21. Donk. B. D. p. 69 PI. XI f. 2. V. H. Syn. 

 p. 73 PL V f. 3, 4. A. S. Atl. XLII f. 8. 



Fresh water (usually larger lakes): Sweden (Lapland to Skane)! Finland (Russian Lap- 

 land to Nyland)! Novaja Zemla! France! Switzerland (Lac Leman)! Japan! New Zealand! America 

 (Canada, Albany, Michigan, "Washington Territory)! 



Var. linearis Cl. — V. linear, not gibbous in the middle, or ends. Area narrower. Striae 

 7 in 0,01 mm. — Finn. maj. "W. Sm. B. D. XYIII f. 162. Nav. maj. var. andesitica Pant. Ill 

 PI. VII f. 113 (1893). 



Fresh water: Sweden (Lake Rosslangen)! Norway (Stavanger, foss.)! England Sm. Finland 

 (Pudasjarvi, foss.)! Holstein! Germany! Africa (Congo, V. H. Coll.)! America (Monticello New 

 York, Waltham Mass., Demerara)! 



Var. heroina A. S. (1876). — V. gibbous in the middle and at the subcuneate ends. L. 0,2 6; 

 B. 0,03 5 mm. Median line broad, oblique. Area narrow. Striae 8 in 0,oi mm. slightly divergent 

 in the middle, and convergent at the ends. Bands indistinct. — Nav. heroina Atl. XLIII f. 2. 



Fresh water: Demerara River! 



Var. asymmetrica Cl. — V. linear, with broad, obtuse ends. L. 0,i4 to 0,26; B. 0,02 to 0,03 

 mm. Median line asymmetrical, the two halves of it meeting each other in an obtuse angle. — 

 PI. I f. 22. 



Fresh water: America (Eralton Lake Canada, Waltham Mass., Crane Pond, Montgomery 

 Alabama) ! 



Var. subacuta Ehb. (1854). — V. linear, with parallel margins and cuneate ends Area 

 narrow. Striae 7 to 7,5 in 0,oi mm. — Pinnul. subacuta Ehb. M. G. XXXV A 6 i. 12. — A. S. 

 Atl. XLIII f. 30 to 32. 



Fresh water: Demerara River! Caldas, Brazil! 



Var. turgidula Cl. — V. strongly gibbous in the middle and at the ends. L. 0,i7 to 0,28; 

 B. 0,034 to 0,04 mm. Striae 7 to 8 in 0,oi mm. 



Fresh water: America (Monticello, Troy, Sierra Nevada)! 



This form is very similar to P. latevittata var. Domingensis, from which it differs only by 

 a narrower band across the striae. 



K. Sv. Vet. Akad. Handl. Band 27. N:o 3. 12 



