KONGL. SV. VET. AKADEMIENS HANDLINGAR. KAND 26. N:0 2. 173 



in 0,01 mm., sliglitly radiate thronglioiit, distinctly punctate. No isolated punetiim below the 

 central nodule. — Grun. in Martelli Florula Bogosensis p. 152 Pl. 1 f. 1, 2. 

 Fresli water: Abyssinia (Grun.). 



54. C. Cistula Hempr. (1828). — V. boat-sbaped, witb concave, centrally slightly gibbous, 

 ventral margin, and truncate or rounded, obtnse ends. L. 0, 07 to 0,i6; B. 0,oi8 to 0,02r) mm. 

 Median line arcuate, broad, bent downwards near the central nodule. The central pores distant, 

 and the terminal fissures reflexed. Axial area narrow, linear, slightly dilated on the dorsal side 

 of the central nodule. Strite 7 to 9 in 0, 01 mm. coarsely lineabe; lineolte 18 to 21 in 0, 01 mm. 

 On the ventral side, near the central nodule, the strite are interrupted by a narrow depression, so 

 that below the central nodule is a segmental row of 2 to 5 puncta. — Bacillaria Cistula Hempr. 

 a. Ehb. Symb. Phys. phyto. Pl. II, IV f. 10. Coccon. Cistula W. Sm. B. D. XXIII f. 221. A. S. 

 Probet. f. l(i Pl. X f. 1—5, 24— 2G. Cymh. Cistula V. H. Syn. p. 64 Pl. II f. 12—13. C. Cistula 

 var. maculata A. S. Atl. LXXI f. 21. Grun. Franz Josephs Land D. p. 07 (45) Pl. I f. 8. C. Cistula 

 var. fusidium Hérib. a. Pbeaö. D. d'Auvergne p. 71 Pl. III f. 12. Coccon. arciicum A. S. Atl. 

 LXXI f 25. Coccon. cornutum, Greg. M. .1. IV Pl. I f. 11 (1856)? 



Fresh and slightly brackish water: Spitsbergen! Norway (Dovre, Stavanger, foss.)! Sweden 

 (Lapland to Skåne), Bay of Bothnia (from Piteå to Uppland and Helsingfors)! Finland! England! 

 Holstein! Belgium! France! Germany! Switzerland! Italy! Mouth of Jenissey! Karatschatka! Japan! 

 Yarkand! America (Winnepeg, Vancouver, Massaehusets, Illinois, California, Mexico)! 



Var. maculata Kutz. (1834). — V. broader and shorter than in the type. L. 0,0 4.'i to0,o82; 



B. 0,013 to 0,015 mm. Striffi 9 to 12 in 0, 01 mm. LineolsB 24 in 0, 01 mm. No row of puncta 

 below the central nodule. — Frustulia maculata Kutz. Dec. N:o 85 (1834) according to Lägst. 

 Cijmh. maculata A. S. Atl. X f. 6; LXXI f. 20, 22. Cyml. Cistula var. mac. V. H. Syn. p. 64 

 Pl. II t 16, 17. Cymh. Bouleana Br. a. Hérib. D. d'Auvergne p. 220 Pl. VI f. 14 1893 (ad spec. 

 auth.). Cymh. Pauli Hérib. a. Perag. D. d'Auvergne p. 70 Pl. III f. 11 (1893). 



Fresh water: Franz Josephs Land (Grun.), Sjntsbergen! Sweden (Vestergötland, Småland)! 

 Finland! England! France! Germany! Greenland! Argentina! 



Var. sihirica Grun. (1880). — V. with rounded, not rostrate ends. L. 0,os; B. 0,024 mm. 

 Median line strongly arcuate. Stria'. 10 (middle) to 12 (ends) in 0,oi mm. lineate (lineokv. about 

 20 in 0,01 mm.) interrupted in the ventral side of the central nodule by a narrow depression. — 

 Coccon. Cistula var. sih. Grun. A. I), p. 25 Pl. I f. 11. 



Fresh water: Mouth of Jenissey! 



Var. arctica Lägst. (1873). — V. boat-shaped, with strongly arcuate dorsal, and slightly 

 concave ventral, margin. Ends truncate. L. 0,o32 to 0, 07 ; B. 0, 007 to 0,oi5 mm. Median line strongly 

 arcuate, broad; its terminal fissures reflexed. Axial area uari-ow. Stria'. 9 to 13 in 0, 01 mm. 

 finely lineate. No row of puncta on the ventral side of the central nodule. — Cymh. variahilis 

 var. arctica Lagst. Spitsb. D. p. 44 Pl. II f. 21. Cymh. arctica A. S. Atl. X f . 12; LXXI f. 23, 24. 



Fresh water: Beeren Eiland (Lagst.), Spitsbergen! Russian Lapland! Mouth of Jenissey! 



Var.? truncata Brun (1880). — V. with sliglitly arcuate dorsal margin, straight ventral margin 

 and very broad, truncate ends. L. 0,045 to 0,o75 mm. StritB 8 to 10 in 0,oi mm. No row of 

 puncta below the central nodule. — Brun D. des Alpes p. 58 Pl. III f. 2. 



Fresh water: Switzerland (Brun.). 



C. Cistula is a very variable species, graduating, as it appears, to C. cymhiformis. Its most 

 distinctive characteristic, the row of puncta below the central nodule, is not present in some of 

 its varieties. The var.? truncata is remarkable for its outline and resembles very mueli the smaller 



C. curta A. Schm. (Atl. IX f. 47. L. 0,02; B. 0,oi mm.) unknown to me. 



55. C. Stuxlbergii Cl. (1880). — V. with strongly arcuate dorsal margin, almost straight 

 ventral margin, and rostrate, truncate ends. L. 0,055 to 0, 075; B. 0, 02 mm. Median line strongly 

 arcuate, with reflexed terminal fissures. Axial area indistinct, slightly dilated on the dorsal side 



