D. JneurTata (fiREG.) Cl. 



Cl. 1. c. p. 84. Xaiirula i. Greg. Micr. Journ. IV. p. 44, pi. V, f. 13. 



A. SCHM. Nords. Diat. pi. I, figs. 10—11; pi. 11, f. 6. 



Frequent: Stamsund + c, Stene r +. 



Distribution: Coasts of the North Sea. Finmark. America. 



D. intfrriipta (Kutz.) Cl. 



Cl. 1. c. p. 84. Xanada i. Kitz. Bacill. p. 100, pi. 29. f. 93. A. Schm. 



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



Somewhat rare: Stamsund r, the Ostnesliord r, Raftsund r, 

 Stene r. 



Distribution: Brackish water. Coasts of the North Sea. 

 F)altic. Arctic regions. The Mediterranean. Red Sea. Inchan 

 Ocean. Pacific Ocean. East coast of America. 



D. lineata (Do.nk.) Cl. 



Cl. 1. c. p. 8.5. Xancula I. Donk. Micr. Journ. VI, p. 32, pi. Ill, f. 17. 



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



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

 Schm. 1. c, occur. 



Distrihution : Coasts of the Nortli Sea. The MediteiTanean. 



D. suhcincta (A. S(HM.) Cl. 

 Cl. 1. c. p. 8(i. Xavkula s. A. Scum. Nords. Diat. pi. II, f. 7. 



Very variable. Structure coarse, coarser than in tiie preceding 

 species. 



Freiiueut: Svolvær r +; the Ostnesflord r -j-, Raftsund r, 

 Stene + c. 



Distribution: Coasts of the North Sea. Arctic reg-ions. The 

 ^lediterranean. Indian Ocean. 



var. media (Geux.) 



Xaviaila honiboides var. media Grun. Arct. Diat. p. 41, pi. Ill, f. .54; Diat. Franz 



Jos. Land pi. I, f. 39 (X. suhcincta). Diiiloneisi cntomon Cl. Synops. Navic. 



Diat. I, p. 87. 



Two, or a few, broad, ii-regular lono-itudinal costte, anastomosing- 

 through oblique ones. 



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

 to D. entumon (cf. under tliat species), by Geunow as a variety 

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

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

 development of longitudinal costæ, and often shows similar peculi- 

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

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

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

 species. 



r also tiiink 1 have seen forms distinctly transitional to A". 

 subciiictK. Such forms are, however, rare. 



Not unfrequent: Stamsund r -(-, the Ostnestiord r -(-, Raft- 

 sund r, Stene r. 



Distrihiitio)i: Arctic regions. 



I), cntomon. 



Regarding the interpretation of tliis name Cl. 1. c. is not (juite 

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

 f. 14, a figure, on whicii the longitudinal costæ 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 Geunow considers them to be D. entomon Eheb. 



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

 media Grun. (in Cl. et Geun. Arct. Diat. p. 41, pi. Ill, f. 541, 

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

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

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

 that form from Franz Jos. 's Land, which Geun. illustrates (Diat. F. J. 

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

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

 mosing ones. 



The figures from A. Schm. Atlas (pi. 1:5, figs. 48—49) refer- 

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

 and which hardly occurs with us. 



D. entomon of Van Heueck Traité p. 195, pi. 26, f. 732 is 

 a different species, identical with A. Schm. Nords. Diat. pi. 1, f. I'>. 

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

 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 D. incurvata, a species which ag^ain is very nearly connected 

 with D. constricta. 



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

 forms passes into D. spkndida, this also shows clearly tiiat his 

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

 Heueck. 



The furrows of D. entomon Cl. answer very well to tliose of 

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



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

 whether they should be referi-ed to D. entomon Cl. (= bomboides 

 var. media Geun.) or D. bomboides. 



D. entomon Eheb. Mikrogeologie pi. 33. XVII, f. 13 has tiie 

 shape of D. constricta, hnt very narrow furrows. D. cntomon Ehrb. 

 1. c. may be Van Heueck's species (A. Schm. Nords. Diat. pi. T, 

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

 have caused the median constriction of the furrows. 



D. splendida (Greg.) Cl. 

 p. 87. Xavicula s. Greg. Micr. Journ. IV, p. 44. 



14. A. SCH.A 



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

 furrows do not swell in the middle and narrow evenly ellipticaliy off 

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

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

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

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

 areoles liere somewhat larger. 



1 have seen no distinct transition between J). splonJida and 

 the other species. 



Somewhat rare: -The Ostnesfiord r-j-, Raftsund r, Stene r +. 



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

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

 Ocean. West Indies. Florida. 



n. homhoides (A. 8< 



, Xariculn h. A. Scum. 



:IIM.) Cl. 

 Nords. Di, 



Similar to the preceding species, but the furrows swell slightly 

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



