KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. Ifil 



witli frustules of tlie same appearance. It seenis then probable tliat the frustules of C. Ccsatii 

 occnv enclosed in gelatinous tubes. 



3. C. angustata W. Sm. (1853). — V. almost symmetrical, witli, usually, slightly triimdu- 

 late margins and capitate ends. L. (),03 to 0,0.') ; B. 0,oo8 mm. Median line almost central, straight- 

 its central pores approximate and its terminal fissures in the ends of the valve. Axial area very 

 narrow or indistinct, not dilated in the middle. Strite about 16 in 0,oi mm., slightly radiate 

 throughout. — iV. angustata W. Sm. B. D. I Pl. XVII f. 156. C. cequalis A. S. Atl. IX f. 69. 

 C. (Bqu. var. hyhrida Grun. A. S. Atl. LXXI f. 50. Navic. incBquilatera Lägst. Spitsl). D. p. 33 

 Pl. II f. 10. 



Fresh water (alpine and arctie regions): Greenland! Spitsbergen! Sootland, England (W. Sm.), 

 Norway (Dovre)!^ Sweden (Gellivara, Degernäs, Loka, Förarm in Asnen, fossil)! Finland (Imandra 

 to Karelen and Åland)! 



4. ('. Schmidtii Grun. (1875). — V. almost symmetrical, broadly lineai', with triundnlate 

 margins and cnneate ends. L. 0,o26; B. 0,009 mm. Median line almost central, slightly flexuose. 

 Axial and central areas indistinct. Strict abont 14 in 0, 01 mm., .'ilightly radiate. — Grun. in 

 A. S. Atl. IX f. 48. 



Brackish water: Nensiedler See, Hungary (Atl.). 



5. C. obtusiuscnla (Kutz. 1844?) Grun. 1875. — V. slightly asymmetrical, broad, almost 

 elliptical, with subrostrate ends. L. 0,027; B. 0,oi2 mm. Median line almost central, straight. 

 Axial area very narrow; centi-al area small and orbicular. Sti-ia; 12 in 0, 01 mm., slightly radiate. 



— KtJTz. Bac. p. 79 Pl. III f. 68. A. S. Atl. IX f. 49. 



Fresh water: Steinitz See (Atl.). 



6. C. alpiua Grun. (1863). — V. slightly asymmetrical, lanceolate, with convex dorsal and 

 ventral margins and slightly obtuse ends. L. 0, 023 to 6,04; B. 0,oo8 to 0, 01 mm. Median line 

 straight, slightlj' excentric. Axial area verv narrow, not dilated in the middle. Striae 5 in 0,oi 

 mm., very slightly radiate, linely transversely lineate. — Grun. Verh. 1863 p. 148 Pl. IV f. 19. 

 A. S. Atl. LXXI f. 44, 45. Brun. Diat. des Alpes p. 62 Pl. III f. 7. 



Fresh water (alpine regions): Tyrol (Grnn.), Switzerland (Brnn), Savoy! 



This little species is very characteristic, not nearly akin to any other Cymhclla, and di- 

 stinguished by its unusually coarse and lineate strise. It is an habitant of alpine regions only. 

 The fine lineation of the strite appears to indicate a relationship to the gronp Kariculce UneolatcB, 

 but there is no clo.sely allied from in that gronp. 



7. C. borealis Cl. (1891). — V. .slightly asymmetrical, linear-lanceolate, gradually tapering 

 from the middle to the obtuse or .slightly capitate ends. L. 0,06 to 0,07; B. 0, 007 to 0, 09 mm. 

 Median line almost central, straight. Axial area very narrow, slightly or indistinctly dilated in 

 the middle. Stria; 10 (middle) to 13 or 14 (ends) in 0, 01 mm., very slightly radiate throughout, 

 very finely lineate. - Cl. D. of Fiul. p. 46 Pl. II f. 19. 



Fresh water: Russian Lapland! 



8. C. delicatiila Kutz. (1849). — V. narrow, lanceolate, slightly asymmetrical, obtuse. L. 

 0,022 to 0,03; B. 0,oof) to 0,006 mm. Strife 18 or 20 (dorsal) to 21 (ventral) in 0,oi mm., delicate. 



— KtJTZ. Sp. Alg. p. 59. A. S. Atl. LXXI f. 54, 55. V. H. Syn. p. 62 Pl. III f. 6. 



Fresh water (moist rocks etc): Norwaj' (Dovre, Brevig)! Sweden (Lajjland to Skåne)! 

 France! Savoy! Geneve! 



This species is recognized by its narrow, almost linear, lanceolate valves and by its close 

 and delicate striae. It is nearly connected with C. Jmvis, which has broader valves and somewhat 

 coarser strige. Intermediate forms exist between both. 



K. Sv. Vet. Akad Haudl. Biinil 26. N:o 2. 21 



