Diatoms. 



215 



There is also a remarkable agreement in their occurrence, as both 

 are mentioned from Campeachy Bay. 



Very rare: Stamsund r+, here in rather large numbers. 



Distribution (of N. sejuncta A. Schm.): West coast of Nor- 

 way (Hvidingso). Campeachy Bay. 



Distribution of N. eugenia A. Schm.: Ceylon. Macassar 

 Straits. Campeachy Bay. 



D. notabilis (Grev.) Cl. 

 Cl. |. c. p. 93. Navicula notabilis Gkev. Micr. Journ. XI. p. 18, f. 9. 



rar. expleta A. Scum. 

 A. Scum- Nords. Diat. pi. 1, 1'. 20, pi. II. 1'. 11. 



Rare: Stamsund r. Raftsund r. Stene r. GaukvaTo r. 



Distribution: Coasts of the North Sea. The Mediterranean. 

 Black Sea. Red Sea. Indian Ocean. Pacific Ocean. West Indies. 

 Brazil. 



D. fusca (Greg.) Cl. 



Cl. 1. c. p. !»:>. Navicula fusca A. Schm. Atlas pi. 7, tigs. 2—3 (var. norvegica 



Cl. 1. c). 



This species is exceedingly variable and includes probably J>. 

 hypei-borea and IK cestiva. Even the limit towards I). Smithii seems 

 not to be reliable. 



Frequent: Moskenstrommen r. Stamsund f. Svolvser -f-, the 

 0stnesfiord r, Raftsund r, Stene r. Gaukvsero +. 



var. Gregorii Cl. 1. o. p. 94. 



Navicula Smithii far f. Greg. Diat. of Clyde IX, f. 15. 



Large, beautiful form. Differs from the main species in the 

 same way as D. major Cl. from D. Smithii. Central nodule elong- 

 ated; terminal nodules distant from the ends. 



Very rare: Stamsund, r. 



Distribution: Coasts of the North Sea. Naples. 



D. hyperborca (Grin.) Cl. 

 Cl. 1. c. p. 95. Navicula hyperborea Grun. Wien Verh. I860 p. 531, pi. III. f. 16. 



Furrows swelling round the central nodule. 

 Rare: Stene r, the 0stnesfiord r. Stamsund r. 

 Distribution: Bohuslan (Sweden). 



rar. excisa A. Scum. 

 Navicula fusca v. excisa A. Schm. Nords. Diat. 



.1. II. f. 9. 



Beautiful and characteristic form. Large, conspicuous pearls as 

 in D. fusca var. Gregorii. 

 Rare: Stamsund, r-f-. 

 Distribution: West coast of Norway. 



D. Smithii (Breb.) Cl. 



Cl. I. o. p. 96. Navicula Smithii Breb. in W. 8m. Brit. Itiat. II. p. 92. 



A. Schm. Atlas pi. 7. tins. It; — 17. 



Exceedingly variable, probably also including D. major and 

 D. borealis. 



Very frequent: Moskenstrommen r, Stamsund c, the Ostnes- 

 fiord r, Raftsund r, Stene c, Gaukva?ro c. 



Distribution: Coasts of the North Sea. Baltic. Arctic regi- 

 ons. The Mediterranean. Indian Ocean. Pacific Ocean. Central 

 America . 



D. major Cl. 



ci,. 1. ••. p. !»<;. Navicula Smithii \. Schm. Atlas, pi. VI I. E. 19. 



Beautiful form, but hardly anything other than a coarse variety 

 of D. Smithii. It seems quite impossible to keep it distinct from 

 large forms of the latter species, with coarser structure. 



The central nodule is usually broadened, broader than the di- 

 stance between the horns, while it, in I). Smithii, is of equal 

 breadth. The terminal nodules are generallj distant from the ends, 

 while they in />. Smithii lie close to them. Both these character- 

 istics are. however, unreliable. Thus forms occur, which, on account 

 of the structure and the terminal nodules, should be referred to 

 J), major, but on account of the form of the central nodule to 1>. 

 Smithii, and vice versa. 



Not unfrequeut : Moskenstrommen +, Stamsund r+, Stene r. 



Distribution: Coasts of the North Sea. The Mediterranean. 

 Indian Ocean. Pacific < Icean. 



D. borealis (Grun.) Cl. 

 Cl. 1. o. p. * * * > - Navicula Smithii rar. borealis Grun. Diat. Franz .I"s. Land 



p. 56, pi. I. f. 4o. 



Furrows swelling round the central nodule. 



Frequent: Stamsund cc. Stene r, the 0stnesfiord r, Gauk- 

 v;ero r. 



M\ specimens differ somewhat from Gbunow's figure, especially 

 in the central nodule, which is not elongated. The double rows 

 of pearls between the costse are very delicate, but are now and 

 then distinctly seen. Agree very well with the description in Gku- 



NOW 1. C. 



Distribution: Sweden (Bohuslan). Arctic regions. Java. 



D. litoralis (Donk.) Cl. 



Cl. 1. c. p. 94. Navicula !. Donk. Brit. Diat. p. 5, pi. I. E. '-'. A. Sum. 



Nords. Diat. pl. 1. figs. 24 — 2b („var. subtilis"). 



Very rare: Stamsund. r. 



Distribution: Coasts of the North Sea. Arctic regions. The 

 Mediterranean. Indian and Pacific Oceans. 



D. nitescens (Greg.) Cl. 



Cl. 1, c. p. 97. Navicula Smithii rar. nitescens Greg. Diat. of Clyde p. 487. 



pl. IX, E. 16. 



Somewhat rare: Stamsund -f-, Stene r, GaukvaTo r. 

 Distribution: Coasts of the North Sea. The Mediterranean. 

 Black Sea. Indian Ocean. Pacific Ocean. Central America. 



1>. Didym.se VH. Synops. 



D. constricta (Grun.) Cl. 



Cl. 1. c. p. 83. Navicula c. Grun. in Wien Verh. 1860, p. 535, pl. III. E. Is. 



N. Donkinii A. Schm. Nords. Diat. pl. I. f. li>. pl. II, t. 8. 



Coarser .structure than in the following species, horns of the 

 central nodule more divergent, and obtuse angles in the lateral 

 contour. At a certain focus, a few very indistinct oblique longi- 

 tudinal costa? are sometimes to be seen. 



Not unfrequent: Stamsund + c, the Ostnesfiord r. Stene r. 



Distributicm : Coasts of the North Sea. Finmark. Balearic 

 Islands. Ceylon. Florida. 



