V, 



ON CONCHOCELIS, A NEW GENUS OF 

 PERFORATING ALGsE. 



IN their interesting account of the plants living in the calcareous shells 

 of molluscs, MM. Bornet and Flahault* mention eight genera of Algae 

 which may be met with in this strange situation. All of these genera 

 are members either of the Cyanopkycecs or Chloropkycecs, and are either 

 bluish or purplish green or grass-green in colour. It was therefore with 

 both surprise and pleasure that I detected among some perforating 

 Algae, extracted from shells which I had gathered near Cumbrae, in the 

 Clyde sea area, some filaments of a beautiful carmine-coloured Alga 

 belonging apparently to the Porphyracea. As Dr. Bornet had devoted 

 so much time and attention to the subject of the perforating Algae, I 

 sent the specimen to him, requesting him to let me know if, during 

 his researches, he had met with anything similar. He at once replied 

 that he had not previously seen anything resembling my plant, which 

 he believed to be a new Alga related to ErytJirotrickia. I propose in 

 the present paper to give a short account of this interesting addition 

 to our marine flora. 



The shells from which this Alga was first obtained were dredged 

 from 6-8 fathoms water off the Tan buoy, between the islands of Great 

 and Little Cumbrae. The best specimens were got in the empty shells 

 of Mya tnmcata and Solen vagina (the common razor-shell). I have, 

 however, subsequently found the same plant, though in poor condition, 

 in many other shells left on the sandy beach by the receding tide. 



To the naked eye the presence of the Alga is betrayed by a pink 

 stain, which cannot be removed by rubbing, on the inner surface of the 

 shells. If a flake, sufficiently thin to be semi-transparent, be broken from 



* ' Sur quelques plants vivant dans le test calcaire des mollusques, par MM. Ed. 

 Bornet et Ch. Flahault.' Bulletin de la Societe botanique de France, vol. xxxvi. 



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