KONGL. RV. VRT. AKADEMIENS HANDLTN0AR."'"bAN1) 27. N:0 3. 81 



Var. ftcalaris Ehb. (1843). — Narrow, linear. Central area a broad transverse fascia. — 

 Stattroptern scalaris Ehb. Am. [V: 2 f. 3. Nar. borcalis var. scalaris Gkun. Verli. 1«(K) p. TjIH 

 PI. IV f. 15. 



Labrador (Ehb.). 



Finn, boreali.s graduates by intermediate forms into P. lata. 



25. P. lata Br^b. (1«38). — V. linear-elliptical, witli broad, rounded ends. L. 0,i to 0,i:!; 

 B. 0,03 to 0,04 mm. Median line oblique; central pores approximate, terminal fissures hook-shaped. 

 Area large, slightly widened in the middle. Strict slightly radiate in the middle, 3 in 0,o 1 mm., 

 transverse at the ends. — Frustulia lata Bri5b. Cons. p. 18. P. lata W. Sm. B. D. I pi. XVIII 

 f. 167. Nav. lata KtJTZ Bac. p. 92. Griin. Franz Jos. Land D. p. 98 PL I f. 14. Nav. lata 

 var. minor H^rib. a. Perag. D. d'Auvergne p. 8() PI. IV f. 5. P. megaloptcra Ehb. M. G. Ill: 1 

 f. 4; IV: 2 f. 5 (1854). Abh. 1870 PL III f. 16. Nar. me(j. H^rib. V>. d'Auvergne p. 88 PL IV 

 f. 6. P. pachyptera Ehb. Am. p. 133 PL IV: 2 f. 9 (1843). Nav. j^ach. A. S. Atl. XLV f. 5, 8. 

 Pant. Ill Pl.XX f. 302. Nav. costata H^rib. D. d'Auvergne p. 87 PL IV f. 7 (1893). 



Fresh water: Franz Josefs Land (Grun.), England! Scotland! Ireland! France (Normandy)! 

 Switzerland! Australia (Murray River)! New Zealand! Hungary fossil. 



Var. Rahenliorstii Grun. (1860). — V. slightly constricted in the middle, with cuneate, 

 truncate ends. L. 0,06; B. 0,oi5 mm. Striie parallel, 4 in 0,oi mm. — Nav. Thuringiaca Rabh. 

 Fl. E. A. p. 205. Nav. Rabenhorstii Grun. Verb. 1860 p. 515, PL IV f. 13. Nav. borcalis var. 

 fossilis Pant. Ill PL V f. 73 (1893). 



Fresh water: Thiiringen (Rabh.). 



Var. latestriata Greg. (1854). ~ V. narrow-linear, with subcuneate extremities. L. 0,o4 to 

 0,06; B. 0,012 mm. Striai 4 in 0,oi mm. — Pirm. latestr. Greg. M. J. II p. 98 PL IV f. 12. 

 Nav. boreali.s var.? proilucta Grun. Verb. 1860 p. 518 PL IV f. 14. 



Fresh water: Mull Dept. 



Var. minor Grun. (1878). — L. 0,04-); B. 0,013 mm. Area narrow. Strife 4 — 5 in 0,(ii mm. 

 — Grun. Cap. S. Alg. PL IV L 22. Fr. Jos. L. I), p. 98 PL I f. 16, 17. Nar. lata V. H. S. 

 p. 76 PL VI f. 1—2. 



Fresh water: Spitsbergen! Franz Jos. Land (Grun.), Casp. Sea (Grun.). 



Var. curta Grun. (1884). — V. elliptical. — Grun. Fr. Jos. L. D. f. 15. 



Fresh water: Franz Jos. Land (Grun.). 



26. P. alpilia W. Sm. (1853). — V. elliptic-lanceolate, with rounded, obtuse ends. L. 0,i 

 to 0,18; B. 0,0.38 to (),((;-> mm. Median line oblique; central nodule large; terminal fissures spirally 

 twisted. Axial area wide (less than \/., of the breadth of the valve) lanceolate. Striae radiate, 3,5 

 in 0,01 mm., transverse at the ends. — B. D. I p. 55 XVIII f. 168. Nav. alpina Donk. B. I), 

 p. 27 IV f. 6. A. S. Atl. XLV f. 1 to 4. 



Fresh water (subalpine regions): Scotland! Ireland! Erzgebirge! Switzerland! 



V. Tabellarieee. 

 Artificial key. 



. Central area with a linear mark on each side of the central nodule 2. 



— without — — — — — — 3. 



o 



I 



{Valve not r 

 — sligh 



Valve not undulate P. stomafophora Grun. 



tly triundulate P- Brandelii Cl. 



., J Valve lanceolate, broad 4. 



\ — linear, narrow 6. 



(Large. L. 0,i4 to 0.i5 mm P Sillimanornm Ehb. 



\ Small. L. 0,04 to 0,07.5 mm 5. 



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



