8 P. T. CLEVE, OX DIATOMS FROM THE ARCTIC SEA. 



else in the arctic sea. This species is widely distributed in 

 almost all seas. 



15. Actinocyclus lulvus (Sm) Ralfs. (Eupodiscus fulvtis 

 Sm Sjn. I pag 24 Pl. IV fig. 40). Spetshergen: Amsterdam 

 Id., Brandwyii Bay. Greenland comraon. Finmarken Grötsund. 



?16. Actinoptychus undulatus (Kg) Ralfs. {Actinocyd.vnd. 

 Sm Syn. I pag. 25, Pl V fig. 43) Spetsbergen Kings Bay 

 (160 ftlis). This species, observed only in the named sample 

 from Kings Bay, I regard as a doubtful arctic species. It is 

 very common in most other seas. 



It abounds on the coast of the Xorth Sea, in the equa- 

 torial seas and is also fonnd near Cape of Good Hope (Gr.) 

 and Magellhaeus Strait (Cl). 



?17. Eupodiscus Argus (Ehb) Sm. (Syn. 1 pag. 24 T. IV 

 fig. 39) Spetsbergen Kings Bay (1(30 fathoms) some few frag- 

 ments. Doubtful as an arctic species. 



?18. Triceratium Favus Ehb. (Sm Syn. I pag. 26 T. V fig. 

 44) Spetsbergen Kings Bay (160 fathoms, very rare). Doubt- 

 ful as an arctic species, * 



19. Trigonium arcticum (Brightw) Cl. {Triceratium arcticum 

 Brightto M. J. I pag. 250 Pl. IV fig. 11. Trigoniiun arctic. 

 Cl Ofvers. K. Vet. Akad. Förh. 1867 pag. 663) Spetsbergen: 

 common ex. gr. Schoal Point. Waijgats Ids. (30—80 fathoms), 

 Treurenberg Bay. Greenland. Finmarken Grötsund. 



This arctic diatom is found also near Beechy Id. Brightw. 

 and according to Grunow near Cape of Good Hope!! 



The F. V. of T. arcticum is in no respects difi'erent from 

 the F. V. of Zygoceros Balsena Ebii., also a very common 

 arctic species, which has exactly the same sculpture of the 

 valve as T. aret. Among the many hundred specimens, which 

 I have seen, I have not seen a single form intermediate be- 

 tween T. arcticum and Z. Bålarna, but still I have some 

 doubts if they really are specifically distinct. The genera Tri- 

 ceratium and Biddulphia &: Zygoceros vary so greatly in outline 

 that I suppose that the many forms, included in those genera 

 may be classed among genera founded on other characters than 

 the outline of the S. V. For instance the Biddulphia Rhombus 

 Ehb and Triceratium striatidum Ehb (= T. BiddulpUa Heib.j 



