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The group Kalyptoraphideæ is new, etablished, as already 

 mentioned, but van Heurck under the name Celoraphidées. The 

 sub-divisions in this group, viz. Eschatoraphideæ, Tropidoraphideæ, 

 €(Onyraphideæ and Brachyraphideæ have been established by nie. 



My group Arraphideæ answers in part to the older group 

 Pseildoraphideæ, a term I do not think appropriate, because a 

 Diatom with three axes has either a raphe, and then belongs to 

 the Raphideæ, or it has no raphe, and then belongs to the Ar- 

 raphideSB; tertium non datur! I have therefore in my description 

 of the species replaced the term Pseudoraphe by the term apical 

 area. 



System of Diatomaceæ Danicæ. 



1. Structure of the valve pinnate, frustule with three axes. Pennatæ 



Schiitt. 2. 

 Structure of the valve concentric, rarliate or irregular, frustule with 

 one, rarely with three axes. Centricæ Schutt. 



± Valve with a raphe. Raphideæ, H. 

 Valve without a raphe. Arraphideæ. 



3. Raphe conspicuous. Euraphideæ. 4. 



Raphe more or less covered. Kalyptoraphideæ.' 5. {Celoraphidées 



V. H.) 



4. Raphe on both valves. Diraphideæ. {Biraphidées V. H.) 



Raphe on hypotheca only (rarely a rudimentary raphe on the apices 

 of the epitheca). Monoraphideæ. {Uniraphidées V. H.) 



5. Raphe long, extending throughout the entire valve. B. 

 Raphe short, developed on the apices only. Brachyraphideæ '-. 



6. Raphe situated along both margins of the valve. Eschatoraphideæ ^ 

 Raphe not situated along both margins of the valve. 7. 



7. The two branches of the raphe extending from apices along the ventral 

 margin of the valve, in the middle ascending towards the dorsal 

 margin and there meeting and formhig an angle. Gonyraphideæ *. 

 Raphe situated upon a keel. Tropidoraphideæ^. 



' Kalyptoraphideæ derivated from xuåutttw, to cover, to veil. 



* Brachyraphideæ — — fipa^og , short. 



^ Eschatoraphideæ — — ia/arog , far distant, situated at the 



edge. 



* Gonyraphideæ — — yåvu , a knee, an angle. 

 = Tropidoraphideæ — — rporug . a keel. 



