Diatoms. 



217 



other parts of the valve. The turrows are also more protracted 

 towards the ends, and not conspicuously crossed by transverse costse 

 at the sides of the central nodule. 



Always easy to distinguish from the preceding species. 



Frequent: Stamsund + c, Brettesnes Skroven r+, Raft- 

 sund r + , Stene r -f-. 



Distribution: Coasts of the North Sea. Alexandria. Indian 

 Ocean. Pacific Ocean. Central America. 



D. didyina (Ehrb.) Eurb. 



Eiiru. Mikrogeolog. pi. 19, f. 32. Pinnularia d. Ehrb. Kreideth. p. 75. Navic- 



tiln didyma A. Schm. Nords. Dial. pi. 1, f. 7. 



Not unfrequent: Moskenstrommen r. Svolvser r+, the Ost- 

 nestiord r, Raftsund r, Stene r. 



Distribution: Especially in brackish water. Coasts of the 

 North Sea. Arctic regions. Baltic. Black Sea. Caspian Sea. 

 Indian Ocean. Pacific Ocean. Cape Horn. West Indies. 



D. bombus Ehrb. 



Ehhb. Mikrogeol. pi. 19, f. 31. Navicula b. Greg. Diat. of Clyde, p. 4S4, 



pi. IX, f. 12. N. gemma A. Schm. Nords. Diat. pi. I, f. 1; pi. II, f. I. 



Frequent: Moskenstrommen r -f-, Stamsund c, Svolvser + , 

 the Ostnestiord r, Raftsund r, Stene -f-, Gaukvsero r +. 



Distribution: Coasts of the North Sea and Western Europe. 

 Finmark. The Mediterranean. Black Sea. Caspian Sea. Indian 

 Ocean. Pacific Ocean. America. 



D. chersonensis (Grun.) Cl. 



Cl. I. c. p. 91. Navicula c. Grun. in A. Schm. Atlas pi. 12, f. 40; pi. 69, f. 21. 



Navicula apis (Do.nk.) A. Scum. Nords. Diat. pi. I, f. 9. 



Not unfrequent: Stamsund -f , Svolvser r, Gaukvsero r. 

 Distribution: Coasts of the North Sea, The Mediterranean. 

 Indian Ocean. Pacific Ocean. West Indies. Florida. 



D. crabro Ehrb. 



Mikrogeol. pi. 19, figs. 29 a, b (non c). A. Schm. Nords. Diat. pi. I. figs. 5—6; 



pi. II. E. 4. D. crabro var. midticostata (Grun.) Cl. I. <■. p. L02. Navicula 



multicostata Grcn. Wien Verb. I860, p. 521. pi. III. f. 13. 



Rather frequent: Moskenstrommen r, Stamsund -)-, the Ost- 

 nestiord +, Raftsund r. Stene r, Gaukvsero r +•■ 



Distribution: Coasts of the North Sea and Western Europe. 

 The Mediterranean. Red Sea. Indian Ocean. Paeitic Ocean. 

 West Indies. 



var. pandura (Breb.) VII. 



Van Heurck Synops. pi. 9, f. 1. Navicula pandura Breb. Diat. Cherb. f. 4. 



A. Schm. Nords. Diat. pi. II. f. :!. 



Peculiar form with tongue-shaped segments. 



Very rare: Gaukvsro, rr. 



Distribution : Coasts of the North Sea and Western Europe. 

 The Mediterranean. Red Sea. Indian Ocean. Pacific Ocean. 

 America. 



FriiMtiilia Aa. 



F. rhomboides (Ehrb.) De Toni. 

 De Toni Syll. p. 277. Navicula rhomboides Ehrb. Amer. pi. 3, 1, f. 15. Van- 

 heurckia r. Breb. Ann. Soc. phyt. Belg. I, p. 204. V. H. Synops. p. 112, pi, 17, 



figs. 1—2. 



Very rare: Svolvser r, Brettesnes— Skroven r. 



Distribution: Fresh water species, rather common. 



St«'iioii«'is inconspicua (Greg.) Cl. 



Cl. Synops. Navic. Dial. I, p. 124. Navicular l. Greg. Dial, of Clyde |> 478 

 pi. 1\. e. :i. N. fistula A. Schm. Nords. Diat. pi. II, f. 29. 



Frequent: Moskenstrommen r. Stamsund r. Gaukvsero -\- c. 

 Distribution: Coasts of the North Sea. Bohuslan (Sweden). 

 Balearic Islands. Arctic regions. 



Trachyneis aspera (Ehrb.) Cl, 

 Cl. Synops. Navic. Diat. I. p. ml. Stauroptera a. Ehrb. Amer. pi. I, figs. 1 — 2; 

 Mikrogeol. pi. 35 A. xxili, f. 13. Navicula n. Van Heurck Synops. pi. X. f. 13 



(rut-, genuina <'l.). 



Common: Moskenstrommen r, Stamsund -f c, Svolvser -f-, 

 the Ostnestiord c, Raftsund r +, Stene c, Gaukvsero -\-. 

 Distribution : ( losmopolitan. 



lla*to°ioia Tiiw. 



M. exigua Lewis. 



Lewis Proc. Ac Nat. Sc. Philad. 186] |). 65, pi. II, f. 5. Van Heurck Synops. 



p. 70, pi. 4. figs. 25—26. 



Very rare: Svolvser, r. 



Distribution: Brackish and marine: Baltic, Belgium. Atlantic 

 coast of America. Behring Island. 



M. Smithii Tiiw. 



W. Sm. Brit. Diat. II. |>. 65, pi. 54. f. 341. Van Heurck Synops. p. 70, 



pl. 4, f. 13. 



Very rare: Svolvser, r. 



Distribution: In brackish water. Baltic. England. Saxony. 

 Caspian Sea. Australia, 



M. apiculata W. Sm. 



W. Sm. Brit. Diat. II. p. 65, pl. 62, f. 387. A. Schm. Atlas pl. 185, f. 43; 



pl. 186. f. 23. 



Very rare: Svolvser, r. 



Distribution: Coasts of the North Sea and Western Europe. 

 The Mediterranean. Black Sea. China. 



17. Cymbellese. 



Cy lube 11a Ac. 



C. eistulct (Hemph.) Kirchn. 



Van Heurck Synops. p. 64. pl. 2. figs. 12—13. 



Very rare: Brettesnes — Skroven, r. 



Distribution: Fresh water species, frequent in arctic, northern 

 or alpine localities. Also in slightly brackish water. 



('. cymbiformis (Ag.?) V. H. 

 Van Heurck Synops. p. 63, pl. II, figs. 11 a — c. 



Very rare: Stamsund r, the Ostnestiord r. 



Distribution: Frequent fresh water species, especially from 

 Northern and Western Europe. Arctic regions Asia, Africa, 

 America and Australia. 



28 



