KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 83 



Var. semicruciata Cl. — Strise in the middle unilaterally interrupted. — Nav. gibha /S 

 Peckii Grun. Verb. 1860 p. 517 PL IV f. 17. 



Fresh water: Sweden (Ojasjo, Blekinge)! Norway (Stavanger Dept.)! America (Canada West., 

 Waltham Mass., Caldas BrazU)! 



Var. interrupta Cl. — Strise interrupted on both sides of the central nodule. — Nav. Stau- 

 roptera Grun. Verh. 1860 p. 516 PI. IV f. 18 (f. gracilis) f. 19 (f. parva) Fr. Jos. Land D. PI. I f. 18. 



A. S. Atl. XLIV f. 41. V. H. Syn. p. 77 PI. VI f. 7, f. 6 (f. parva). Nav. Tabellaria V. H. Syn. 

 f. 8. Nav. alaujensis Pant. II p. 41 PL III f. 54 (1889). 



Fresh water: Franz Josefs Land (Grun.), Sweden! Finland! Norway! Scotland! France 

 (Lac Gerardmer Vosges)! New Zealand! Hawaii! Demerara! Surinam! North America (Waltham 

 Mass., Troy, New Hampshire)! Ecuador! 



Var. sancta Grun. Ms. — V. strongly gibbous in the middle. L. 0,ii; B. O.ois mm. Area 

 very wide. Strise 10 to 11 in 0,oi mm. 



Fresh water: Santos, Brazil! Bengal! 



31. P. rangoonensis Grun. Ms. — V. linear, with broad, rounded ends. L. 0,o7 to 0,io; 



B. 0,012 to 0,014 mm. Median line filiform, with approximate central pores and comma-like, ter- 

 minal fissures. Axial area distinct, but narrow, in the middle dilated to an elliptical space, or on 

 one or both sides, to a transverse fascia. Strise 8 to 10 in 0,oi mm. divergent m the middle, con- 

 vergent at the ends. — Stauroptera semicruciata Ehb. M. G. XXXIII: 2 f. 7*? 



Fresh water: Rangoon! 



This form is scarcely specifically distinct from P. stauroptera. The same is also the case 

 with Nav. Troyana Grun. (in Cl. and Moller Diat. N:o 275) and Nav. Forarmensis Grun. (CL and 

 Moller Diat. N:o 140), which I am unable to distinguish from P. rangoonensis. The only diff'e- 

 rences between these forms and P. stauroptera consist in the shape of the valve and in the term- 

 inal fissures, which are more curved in P. rangoonensis. I hav efound such forms from the following 

 localities: Greenland, Sweden (Forarm, Smaland), Troy (New Hampshire), Demerara River, New 

 Zealand, Blue Mountains (Australia). 



32. P. Brandelii Cl. (1891). — V. linear gibbous in the middle and at the ends, often 

 with tri-undulate margins. Ends broadly rounded, frequently subclavate. L. 0,07 to 0,08; 

 B. 0,007 to 0,009 mm. Median line filiform, with semicircular terminal fissures. Area distinct, 

 narrow, linear, in the middle widened to a broad transverse fascia, having a linear marking on 

 each side of the central nodule. Strise 14 in 0,oi mm., divergent in the middle, convergent at 

 the ends. - D. of Finl. p. 26 PL 1 f. 8, 9. 



Fresh water: Sweden (Almten in Kalmar Ian)! Finland! France (Lac Gerardmer, Vosges)! 



33. P. stomatophora Grun. (1876). — V. linear-lanceolate, gradually tapering from the 

 middle to the rounded ends. L. 0,o7 to 0,ii; B. 0,o9 to 0,oii mm. Median line with bayonet- 

 shaped terminal fissures. Axial area narrow, linear, widened in the middle to a narrow trans- 

 verse fascia, where is on each side of the central nodule a linear marking. Strise 12 to 13 in 

 0,01 mm., strongly divergent in the middle and convergent at the ends. — Nav. stomatophora 

 Grun. in A. S. Atl. XLIV f. 27 to 29. 



Fresh water: Iceland, Scotland (Island of Lewis)! Norway (Dovre, Atl.)! Sweden (Ross- 

 langen in Kalmar Ian)! Finland! Germany (Harz, Atl.), New Zealand! America (Canada, Crane 

 Pond, French Pond)! 



Var. continua Cl. — L. 0,07 to 0,12; B. O.oos to 0,oi4 mm. Strise 13 in 0,oi ram., not 

 interrupted. 



Fresh water: Loch Kinnord, Scotland! Sweden (Lake Rosslangen in Kalmar Ian)! 



34. P. bogotensis Grun. (1876). — V. linear, with rounded ends. L. O.i to 0,ii; B. 0,oi3 

 mm. Median line with approximate central pores and bayonet-shaped terminal fissures. Axial 



