797 



chcete ferox, Cladophora riipestris, ''-'C. serlcea, Plectonenia norvegiciim 

 and ■Spiriilina siihsalsa. If we add these to the ahove-mentioned 

 numher\ we have 143 species. Of these, 111 are also found at 

 the Faeroes. Tlius North-East Iceland has 23 species less in com- 

 mon with the Faeroes than South -West Iceland. 



Firstly, as to the 32 species found at North- East Iceland and 

 not at the Faeroes, they may be divided into the following groups: 



I. The Arctic group: Tiirnerella Pennyi, Delesseria Baerii, Po- 

 lysiphonia arctica, Lithothamnion flavescens, L. foecundiim, Om- 

 phalophyllum iilvaceiim, Dictyosiphon corymbosum, Laminaria 

 nigripes and Monostroma groenlandiciim; 9 species in all. 

 II. The Subarctic group: 



Subdivision 1: Peyssonnelia Rosenvingii, Lithothamnion tophi- 

 forme, Ralfsia deiista, R. ovata, Coiledesme bnlligera, Saccorhiza 

 dermatodea, Ulothrix snbflaccida, Pseudendoclonium marinum, 

 Urospora Hartzii, Acrosiplionia penicilliformis ; 10 species in all. 

 Subdivision 2: Phceostroma piistulosum, Chlorochytrinm derma- 

 tocolax; 2 species in all. 



III. The Boreal-arctic group: Chantransia microscopica. 



IV. The Gold-boreal group: Petrocelis Hennedyi, Lilhothamnion 

 norvegicum, Ascocyclns islandiciis, Ectocarpiis penicillatus, Spha- 

 celaria radicans, Dictyosiphon Mesogloia, D. Chordaria, Entero- 

 morpha aureola, Ochlochcete ferox, Plectonema norvegicum; 10 

 species in all. 



If w^e compare these species with those that are not common 

 to South -West Iceland and the Faeroes, we at once perceive a very 

 distinct difference in that the arctic group is much increased^. 

 It is not likely that any of these 9 species will be found at the 

 Faeroes; and as to the subarctic species of the subdivision 1, it is 

 likewise improbable that they will be found there, a few species 

 perhaps excepted. On the other hand the species of subdivision 2 

 may probably also be found on the Fseroese coasts, and this is cer- 

 tainly also the case wdth the greater part of the cold-boreal species. 



^ It is, however, doubtful, whether the}' may all be found at North and East 

 Iceland proper; the 8 species marked with asterics and which have all been found 

 much farther north, for instance at Greenland, must, however, be supposed to occur 

 at North Iceland, and especially at East Iceland. 



■^ This group will most probabh' be still more increased on renewed inve- 

 stigations, as we may certainly suppose, that the two arctic species at any rate, 

 Cruoria arctica and Ceratocolax Hartzii, found at the other side of Hornbjarg, also 

 grow there. 



51* 



