KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 167 



Var. suhroslrata Cl. — V. with scarcely rostrate, obtuse ends. L. 0,i9 to 0,2o; B. 0,o45 

 mm. Strise 9 in 0,oi mm. coarsely punctate; puncta 9 to 13 in 0,o] mm. — Cymb. heteropleura 

 A. S. Atl. IX f. 3. 



Fresh water: Canada! Danas Pond! Cherryiield! 



Var. minor Ch. — V. with rostrate and truncate ends. L. 0,06 to 0,08; B. 0,oi5 to 0,022 

 mm. Strife 9 in 0,oi mm., coarsely punctate; puncta 18 to 21 in 0,oi mm. — Cymh. Ehrenb. var. 

 Lagst. Spitsb. D. p. 42 PI. II f. 17. Cymi. A. S. Atl. IX f. 51, 52. 



Fresh water: Spitsbergen! Beeren Eiland (Lagst.), Xorway (Dovre)! Scotland (Lough Monrne, 

 foss.)! Jenissey! St. Flora, Italy (foss.)! 



The typical C. heterojyJnira is a large and characteristic boreal form. The var. minor occurs 

 at Hjerkin in Dovre and cannot be distinguished from specimens in St. Flora deposit. The latter 

 variety differs from C. cuspidata in nothing except the somewliat different shape of the ends and 

 the more coarsely punctate strise. C. americana A. S. (Atl. IX f. 15, 20) seems to be intermediate 

 between C. cuspidata and G. heteropleura var. minor. A similar form occurs in New Zealand at 

 Horawarra. 



32. C. oregoiiica Cl. N. Sp. — V. slightly asymmetrical, lanceolate, gradually tapering 

 from the middle to the acute ends. L. 0,i ; B. 0,02 mm. Median line almost central. Axial area 

 narrow, slowly dilated to the middle, where it suddenly expands to a large, subrectangular, central 

 area. Strise 17 (middle) to 20 (ends) in 0,oi mm. radiate throughout, punctate; puncta about 18 

 in 0,01 mm. forming longitudinal rows. — PI. IV f. 25. 



Fresh water: Oregon, fossil! 



33. C. Molleriana Grun. (1875). — V. nearly symmetrical, somewhat irregularly lanceolate, 

 ol)tuse. L. 0,05 to 0,06; B. 0,oi to 0,oi2 mm. Terminal nodules of the median line at some di- 

 stance from the ends. Axial area narrow; central area large, orbicular. Striae 12 to 13 in 0,oi 

 mm., radiate throughout. — Grun. in A. S. Atl. IX f. 71 to 75. 



Fresh water(?): "Wedel in Holstein (Atl.). 



It seems doubtful whether this form, which I know only from the figures in A. S. Atlas, 

 really be a Cymbella. It has more of the appearance of some form belonging to the group of 

 Navicula viridula, but the striae are radiate at the ends. 



34. C. (Encyon&ma) laciistris Ag. (1824). — V. lanceolate, scarcely asymmetrical, with 

 obtuse or truncate ends. L. 0,03 to 0,o6; B. 0,oi mm. Median line nearly central; its terminal 

 nodmles very distant from the ends. Axial area narrow; central area small, irregular. Strise 

 about 9 in 0,oi mm., divergent in the middle, convergent at the ends, in the middle alternately 

 longer and shorter, transversely lineate; lineolae about 28 in 0,oi mm. — Schizonema lacustre Ag. 

 Syst. p. 10. A. S. Atl. LXXI f. 1 to 5. V. H. Syn. PI. XV f. 40. CoUetonema subcoherens 

 Thwaites in W. Sm. B. D. II p. 70 PI. LVI f. 353. Encyonema Ungeri Grun. in A. S. Atl. X 

 f. 63. CoUetonema lacustre V. H. Syn. p. 111. 



Fresh or slightly brackish water: Hungary (Plattensee Cl. M. D. N:o 108), England (W. Sm.), 

 Gulf of Bothnia! 



The frustules of this species live enclosed in mucous tubes. The structure of the valve 

 shews that it is nearly akin to the Naviculse lineolatse. 



35. C. (Encyonema) prostrata Berk. (1832). — V. strongly asymmetrical, semielliptical, 

 with obtuse ends, frequently inclined downwards. L. 0,04 to 0,i; B. 0,o25 to 0,03 mm. Median 

 line straight; its terminal nodules considerably distant from the ends. Axial area narrow; central 

 area small, orbicular. Striae about 7 in 0,o\ mm., in the middle of inequal length, and radiate at 

 the ends convergent, transversely lineate. — Monetna prostratum Berk. Brit. Alg. PI. IV f. 3. 

 Gloeonema Leibleinii Ag. Consp. p. 31? Encyonema paradoxum KtJTZ. Bac. p. 82 PI. XXII f. 1 

 (1844). Encyon. prostratum Ralfs Ann. X. Hist. (I) XVI PI. XVIII f. 3 (1845). W. Sm. B. D. n 



