■J 1 6 



E. Jersense i. 



D. incnrrata (Greg.) Cl. 



Cl, 1. c. p. 84. Navicula i. < ;heg. Micr. Joum. IV. p. 41, pi. V, f. 13. 



A. Schm. Nords. Diat, pi. T, figs. 10—11; pi. II. f. 6. 



Frequent: Stamsund + c, Stene r+. 



Distribution: ('oasts of the North Sea. Finmark. America. 



D. interrupts (Kutz.) Cl. 



Cl. 1. c. p. 84. Navicula i. Kutz. BaciU. p. 100. pi. 29, f. 93. A. Schm. 



Nords. Diat. pi. I, f. 8. 



Somewhat rare: Stamsund r. the Ostnestiord r. Raftsund r, 

 Stene r. 



Distribution: Brackish water. Coasts of the North Sea 

 Baltic. Arctic regions. The Mediterranean. Red Sea. Indian 

 l icean. Pacific Ocean. East coast of America. 



D. lineata (Done.) Cl. 



Cl. 1. c. p. 85. Navicula I. Dome. Micr. Joum. VI, p. 32, pi. III. f. 17. 



A. Schm. Nords. Diat. pi. I, figs. 16—17. 



Rare: Stamsund r, Stene r. Both forms illustrated by A. 

 Schm. 1. c, occur. 



Distribution: (.'oasts of the North Sea. The Mediterranean. 



D. sabcineta (A. Schm.) Cl. 

 Cl. 1. c. p. 86. Navicula s. A. Schm. Nords. Diat. pi. II. f. 7. 



Very variable. Structure coarse, coarser than in the preceding 

 species. 



Frequent: Svolvser r+, the 0stnesfiord r+, Raftsund r, 

 Stene -f- c. 



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

 Mediterranean. Indian Ocean. 



rar. media (Grun.) 

 Xftricitln Imnihoiilc* cm: matin Grun. Arct. Diat. p. 41, pi. III. t. 54: Diat. Franz 

 Jos. Land pi. I, f. 39 (N. subcincta). Diploneis entomon Cl. Synops. Navic. 



Diat. I, p. 87. 



Two. or a few, broad, irregular longitudinal costse, anastomosing 

 through oblique ones. 



This form is very remarkable. By Cleve it has been referred 

 to D. entomon (cf. under that species), by Gruno-w as a variety 

 to D. bomboides. Grun. has, however, noted the close relationship 

 to D. subcincta. As this species is very variable as regards the 

 development of longitudinal eostse, and often shows similar peculi- 

 arities as the present variety, I have thought it best to consider 

 the latter a variety of D. stibcincta, though it is, on the whole, 

 so characteristic that it might very well be regarded as a separate 

 species. 



1 also think L have seen forms distinctly transitional to X. 

 subcincta. Such forms are, however, rare. 



Not unfrequent: Stamsund r +, the Ostnestiord r -}-, Raft- 

 sund r, Stene r. 



Distribution: Arctic regions. 



D. entomon. 



Regarding the interpretation of this name Cl. 1. e. is not quite 

 clear. His species seems to be = A. Schm. Nords. Diat. pi. I, 

 f. 14, a figure, on which the longitudinal eostse are very indistinct. 

 Cl. quotes, however, also A. Schm. 1. c, f. 13, a figure which 



undoubtedly represents another species. A. Schm. himself remarks 

 that these two figures cannot be referred to the same species, but 

 that Grunow considers them to be D. entomon Eheb. 



Cleve's species is partly identical with D. bomboides var. 

 media Grun. (in Cl. et Gurx. Arct. Diat. p. 41, pi. Ill, f. 54), 

 a form, which, according to Gruxow, is an intermediate one be- 

 tween D. bomboides and subcincta. This var. media I have referred 

 to D. subcincta (cf. above). It is hardly essentially different from 

 that form from Franz .los.'s Land, which Grux. illustrates (Diat, F. J. 

 L. pi. I, f. 39) as Navicula subcincta. In this figure the irregular 

 ramification of the longitudinal eostse is seen, producing two anosto- 

 mosint:' ones. 



The figures from A. Schm. Atlas (pi. 13, figs. 4S— 49) refer- 

 red to by Cl. 1. c. represent a species, which I have not seen, 

 and which hardly occurs with us. 



D. entomon of Van Heurck Traite p. 195, pi. -J(i. f. 732 is 

 a different species, identical with A. Schm. Nords. Diat, pi. I. f. 13. 

 This figure seems, however, to represent a form of D. eonstrieta. 

 The furrows, especially, answer very well to the latter species. 

 Van Heurck who is on the whole conservative on the question of 

 species, also mentions the near relationship between D. entomon 

 and J>. incurvata, a species which again is very nearly connected 

 with D. eonstrieta. 



When Cleve 1. c. remarks that D. entomon by intermediate 

 forms passes into J). splendida, this also shows clearly that his 

 species is different from that of A. Schmidt (f. 13) and Van 

 Heurck. 



The furrows of 1>. entomon Cl. answer very well to those of 

 D. bomboides, less so to those of D. splendida. 



I have, however, never seen specimens where it was doubtful, 

 whether they should be referred to D. entomon Cl. (= bomboides 

 var. media (iurx.i or I>. bomboides. 



D. entomon Ehrb. Mikrpgeologie pi. 33. XVII, f. 13 has the 

 shape of D. eonstrieta, but very narrow furrows. /'. entomon Ehrb. 

 1. c, may be Van Heurck's species (A. Schm. Nords. Diat. pi. I. 

 f. 13): the specimen seems to lie somewhat obliquely, which may 

 have caused the median constriction of the furrows. 



D. splendida (Greg.) Cl. 



Cl. 1. c. p. 87. Navicula s. Greg. Micr. Journ. IV, p. 44, pi. V, f. 14. A. Schm 



Nords. Diat. pi. I, figs. 3—4: pi. II, E. 2. 



This beautiful species is very similar to D. bomboides, but the 

 furrows do not swell in the middle and narrow evenly elliptic-ally off 

 towards the ends. The eostae. besides, distinctly cross the furrows at 

 the sides of the central nodule (i. e., in the furrows are here distinct 

 transverse eostae), while these furrows else are almost smooth. The 

 median structure of the valve generally is a little coarser, the 

 areoles here somewhat larger. 



I have seen no distinct transition between D. splendida and 

 the other species. 



Somewhat rare: The Ostnestiord r-f, Raftsund r. Stene r -f-. 



Distribution: Coasts of the North Sea. Arctic regions (Fin- 

 mark. Baren Eiland, Spitsbergen, Greenland). Indian Ocean. Pacific 

 Ocean. West Indies. Florida. 



D. bomboides (A. Schm.) Cl. 

 Cl. 1. c. p. 88. Navicula b. A. Schm. Nords. Diat. pi. I, f. 2. 



Similar to the preceding species, but the furrows swell slightly 

 round the central nodule, and the structure here is like that of the 



