KONGL, SV. VKT. AKADKMIKNS IIANDMNCJAK. HANI). 27. N:() 3, 77 



11. P. globicops (xREii. (1«56). — V. strongly gibbous in the middle and with capitate 

 ends. L. 0,();i to (),oi; B. 0,01 mm. Axial area indistinct; central area a broad, transverse fas(^ia. 

 narrowed towards the margin. HtriiB 16 to 18 in 0,01 mm., divergent in the middle, convergent 

 at the ends. — M. J. IV PI. I f. 34. Nav. (jlob. V. H. S. Syn. Suppl. A. f. \H. 



Brackish water: Scotland (dreg.), Anvers (V. H.), Strehlen (Grun.), Dfii'renberg in Saxony! 

 Bengal! 



Var. Kroolcii Grun. (1882). — L. 0,(ii.') to (J, 028; B. 0,00.5 to (»,oo7 mm. Central area a wide 

 lanceolate space. Striae 15 to 17 in 0,oi mm. in the middle, 10 to 20 near the ends. — Nav. 

 Krockii Grun. Foss. D. Osterr. ling. p. 155 PI. XXX f. 40. 



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



12. P. inicrostauron Ehb. (1843). — V. linear, with parallel margins and rostrate, bi'oad 

 ends. L. 0,025 to 0,o8; B. 0,oo7 to 0,oo9 mm. Axial area very narrow, frequently dilated in the 

 middle to a transverse fascia. Stria; 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. KtJTZ. Bac. p. lOH PI. XXIX f. 13. A. S. Atl. XLIV f. 16. Nav. diverf/cm 

 f. minor A. S. Atl. XLIV f. 14, 34, 35, XLV f. 31 to 34. Nor. Brehissonii v. subproducta V. H. 

 Syn. p. 77 PI. V f. 9. Pinn. inierrupta Pedicino Ischia II f. 14. Nav. hicapitata var. hybrida 

 V. H. Syn. PI. VI f. 9. Nav. Brcbis.sonii Lagst. Spitsb. D. I f. 2 a. Pinn. liabenhorstiana Hilse 

 Rab. A. Sachs. N:o 842 (1859). Nav. divergens var. prolonyata Br. a. Hi5ribaud D. d'Auvergne 

 p. 89 PI. IV f. 1. 



Fresh water: Spitsbergen! Finmark! Sweden (Lappland, Areskutan, Skane)! Finland (La})p- 

 land to Abo)! England! Germany! Kamtschatka! Australia (Blue Moiintains)! Greenland! North 

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



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

 formis, which graduates into P. nwsolcpta. 



III. Divergentes. 

 Artificial key. 



I 



^ . Terminal Assures in contrary direction P. platycephala Ehb. 



in the same direction 2. 



I Valve with undulated margins P. Legunien Ehb. 



\ — not undulated 3. 



Central area rounded P. karelica Cl. 



a transverse fascia 4. 



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



4. 



„ |. Central area r 



{ 



Larger forms 0.0 7 to 0,.S6 mm 6. 



j Striffi very strongly divergent P. divergentissima Grun. 



' \ — somewhat divergent P. Brebissonii KiJTZ. 



( Strise 8 to 9 in 0,oi mm 7. 



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



) Valve linear with parallel margins 8. 



I Valv 



I — — gibbous in the middle and at the ends P. Hartleyann Greg. 



( Striae strongly radiate P. episcopalis Cl. 



I — slightly radiate P. Cardinaliculus Cl. 



13. P. divergentissima Grun. (1880). — V. lanceolate with obtuse ends. L. O.os to 0,0.3,5; 

 B. 0,007 mm. Axial area indistinct. Central area a broad fascia. Striw 13 in 0,oi mm. strongly 

 divergent in the middle and convergent at the ends. — Nar. nodulosa forma Lagst. 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. 



