Tliere is also a remarkable airreeineiit in tiirir orciinriicc. as l)i)tli 

 are iiientioncil from Campeaehy l!a\. 



Very rare: Stamsund r-|-, here in rather larye iuimbor.s. 



DhtrihKtion (of X scjtnicta A. .Siii.m.): West eoast of Nor- 

 way (Hvidingsø). Campeaehy 15ay. 



Dhtribiition of X. engeuiu A. Scum.: Ceylon. Macassar 

 Straits. Campeaehy P.ay. 



D. notnbilis ((iKi:v.) Ci.. 

 c. u. 113. yaviada votabilis Grev. Jlicr. .Joiini. XI 



rar, expleta A. Shim. 

 \. SciiM. Nonls. Diat. pi. I, I. -JO. pi. II, (. 11. 



Kare: Stamsuml r, Raftsund r, Stenc r. (iauUv;ero r. 



Distribitfion: Coasts of tlic Nortii Sea. The Mediterranean. 

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

 Brazil. 



D. ftisca (GKF.ci.) Ci 

 93. yiicicula fusca A. Schm. Atlas p 



tigs. 2—3 (far. norvegica 



This species is exceedingly variable and includes probably D. 

 hyperborea and D. miiva. Even the limit towards D. Smithii seems 

 not to be reliable. 



Frequent: Moskcnstrommen r, Stamsund +, Svolv;er +. the 

 Østnestiord r. Raftsund r, Stene r, Gaukva-ro -(-. 



rar. Gregorii Ci,. 1. c. p. 94. 

 Nnv'irula SmMii var f. Greg. Diat. of Clyde IX, f. 15. 



Ijarge, beautiful foi'oi. Dillers from the main species in the 

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

 ated; terminal nodules distant from the ends. 



Very rare: Stamsund, r. 



Distribittion: Coasts of the North Sea. Naples. 



D. byperborea (Gbun.) Cl. 

 Cl. 1. c. p. 9,i. Xadcula hyperborea Grun. Wien Verb. 18H0 p. .531. pl. III, f. 16. 



Furrows swelling round the central nodule. 

 Rare: Stene i', the Ostnesfiord r, Stamsund r. 

 Distribution: Bohuslan (Sweden). 



y.avicula /h 



rar. excisa A. Schm 

 excisa A. Schm. Nurds 



Beautiful and characteristic form. Large, conspicuous pearls as 

 in D. fusca var. Gregorii. 

 Rare: Stamsund, r^-- 

 Distribution: West eoast of Norway. 



D. Smithii (Breb.) Cl. 



Cl. 1. c. p. 9«. Xaricuhi SiHitliii Breb. in W. Sm. Brit. Diat. II. p. 9ii. 



A. Scum. Atlas jil. 7, tigs. Iti— 17. 



Exceedingly variable, probably also including I), major and 

 D. borealis. 



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

 fiord r, Raftsund r, Stene c, Gaukværo c. 



Distribution: Coasts of the North Sea. 15altic. Arctic regi- 

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

 America. 



J), major Ol. 



I 'I.. 1. (■ p. iM>. .\'(irii;iiln Sntillni \. Schm. Atlas, pi. VII, f. U». 



lleautiful form, but hardly anything other than a coarse variety 

 of J). Sniilhii. It seems quite impossible to keep it distinct from 

 large forms of the latter .species, witii coarser structure. 



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

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

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

 while they in D. Smithii lie close to them. Hotli these character- 

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

 of the structure ami tiie terminal nodules, should be refen-ed to 

 D. major, but on account of the form of the central nodule to /I 

 Smithii, and vice versa. 



Not unfrequent : Moskenstrommen +, Stamsund r H. Stene i-. 



Distribution: Coasts of the North Sea. The Mediterranean. 

 Indian Ocean. Pacific Ocean. 



D. borealis (Gru.n.) Cl. 



Cl. 1. C-. p. 91). Xariaila Siiiithii var. hnrealis Gm n. Diat. Franz .Jus. Land 



11. ofi, pi. I. f. 40. 



Furrows swelling round the central nodule. 



Frequent: Stamsund cc. Stene r. the Ostnesfiord r. (laiik- 

 væro r. 



My specimens differ somewhat from Gkuxow's figure, especially 

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

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

 then distinctly seen. Agree very well with the descrijition in Grc- 

 NOW 1. c. 



Distribution: Sweden (P>ohuslan). Arctic reLrions. .lava. 



D. litoralis (Doxk.) Cl. 



Cl. 1. c. p. 94. Xavirida I. Donk. Brit. Diat. p. 5, pi. I, f. 2. A. StHM. 



Nords. Diat. pi. I. tigs. 24—25 (..rar. .<:„lillli.-<" ). 



Very rare: Stamsund, r. 



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

 Mediterranean. Indian and Pacific Oceans. 



D. nitescens (Greo.) Cl. 



Cl. 1. !■. p. 97. Xaviruln Siiiifliii var. nitescois Gheg. Diat. of Clyde p. 487. 



pi. IX. f. Ui. 



Somewhat rare: Stamsund -f, Stene r, Gaukv;cro r. 

 Distribution: Coasts of the North Sea. The Mediterranean. 

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



b. Didymæ VH. Synops. 



D. constricta (Grun.) Cl. 



Cl. 1. c. 1). 83. Xavicula c. Grun. in Wien Verb. 18»i0, )i. 535, pi. Ill, f. IS. 



iV. Donkinii A. Schm. Nords. Diat. pi. I. f. 12, jil. II, f. 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 lon.gi- 

 tudinal costæ are sometimes to be seen. 



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



Distriliation : Coasts of the North Sea. Finmark. Balearic 

 Islands. Cevlon. Florida. 



