KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND. 27. N:0 3, 77 



11. P. globiceps G-REG. (1856). — V. strongly gibbous in the middle and with capitate 

 ends. L. 0,03 to 0,o4; B. 0,oi mm. Axial area indistinct; central area a broad, transverse fascia, 

 narrowed towards the margin. Striae 16 to 18 in 0,oi mm., divergent in the middle, convergent 

 at the ends. — M. J. IV PI. I f. 34. Nav. glob. V. H. S. Syn. Suppl. A. f. 13. 



Brackish water: Scotland (Greg.), Anvers (V. H.), Strehlen (Grun.), DSrrenberg in Saxony! 



Var. Kroohii Grun. (1882). — L. 0,oi5 to 0,o28; B. 0,oo5 to 0,oo7 mm. Central area a wide 

 lanceolate space. Striae 15 to 17 in 0,oi mm. in the middle, 19 to 20 near the ends. — Nav. 

 Krockii Grun. Fobs. D. X>sterr. Ung. p. 155 PI. XXX f. 40. 



Brackish water: Hungary, (Soos Dept. Grun.), Gulf of Bothnia (Salmis to Tornea)! 



12. P. microstanron Ehb. (1843). — V. linear, with parallel margins and rostrate, broad 

 ends. L. 0,025 to 0,08; B. 0,oo7 to 0,oo9 mm. Axial area very narrow, frequently dilated in the 

 middle to a transverse fascia. Striae 12 in 0,oi mm., strongly divergent in the middle and con- 

 vergent at the ends. — Stanroptera microstauron Ehb. Am. I: 4 f. 1; IV: 2 f. 2, Microg. XVI: 2 

 f. 4. Stauroneis micr. Kutz. Bac. p. 106 PI. XXIX f. 13. A. S. Atl. XLIV f. 16. Nav. divergens 

 f. minor A. S. Atl. XLIV f. 14, 34, 35, XLV f. 31 to 34. Nav. Brehissonii v. subproducta V. H. 

 Syn. p. 77 PI. V f. 9. Finn, interrupta Pbdicino Ischia II f. 14. Nav. bicapitata var. hybrida 

 V. H. Syn. PI. VI f. 9. Nav. Brebissonii Lagst. Spitsb. D. I f. 2 a. Finn. Rabenhorstiana Hilse 

 Rab. A. Sachs. N:o 842 (1859). Nav. divergens var. prolongata Br. a. H^ribaud D. d'Auvergne 

 p. 89 PI. IV f. 1. 



Fresh water: Spitsbergen! Finmark! Sweden (Lappland, Areskutan, Skane)! Finland (Lapp- 

 land to Abo)! Englandi^ermany ! Kamtschatka! Australia (Blue Mountains)! Greenland! North 

 America (Canada, Maine, white Mountains, Sierra Nevada)! 



P. microstauron is closely connected with P. Brebissonii and P. interrupta var. stauronei- 

 formis, which graduates into P. mesolepta. 



III. Divergeutes.. 



Artificial key. 



^ j Terminal fissures in contrary direction .P. platycephala Ehb. 



\ — — in the same direction .... . . . 2. 



Valve with nndnlated margins P. Legumen Ehb. 



not nndnlated 3. 



i Central area rounded ... P. karelica Cl. 



"■ \ ^ — a transverse fascia . . 4. 



( Small forms 0,04 to 0,06 mm. . . . . 5. 



I Larger forms 0.07 to 0,36 mm. . .... 6. 



( StrisB very strongly divergent ... ... P. divergentissima Gbun. 



■ \ — somewhat divergent . P. Bribissonii Kutz. 



I Stris 8 to 9 in 0,oi mm 7. 



\ — 11 to 12 in 0,01 mm . . P. divergens W. Sm. 



j Valve linear with parallel margins 8. 



' \ — — gibbons in the middle and at the ends ... P. Bartleyana Gbeg. 



f StrisB strongly radiate P. episcopcdis Cl. 



\ — slightly radiate ... .P. Cardinaliculus Cl. 



13. P. divergentissima Grun. (1880). — V. lanceolate with obtuse ends. L. 0,o3 to 0,035; 

 B. 0,00 7 mm. Axial area indistinct. Central area a broad fascia. Striae 13 in 0,oi mm. strongly 

 divergent in the middle and convergent at the ends. — Nav. nodulosa forma LAG^ST. Spitsb. D. 

 p. 22 PI. II f. 2. Nav. divergentissima Grun. in V. H. Syn. PI. VI f. 32. 



Fresh water: Spitsbergen (Ldt), North Iceland! Norway (Dovre)! Finland (Russian Lap- 

 land, Abo)! Greenland! Canada! New Zealand! 



This little species is very characteristic and seems to belong to arctic and alpine regions. 



'i' 



