16 158 Proceedings of the Royal Irish Academy. 



{n) Additions to the British Ides. — With regard to these, the following 

 nine are inconspicuous species whirl) are probably to be found in England 

 and Scotland if carefully searched for: — 



Phormidium persicinum. Ulothrix pseudoflacca. 



1'. Bubuliferum. Dichosporangium Chordariae. 



Lyngbya confervoides. Petroderma raaculans. 



Symploca dubia. Chantransia Thuretii. 

 Ulothrix subtlaccida. 



Of the remainder: — 



Calothrix mdophytica sp. nov., is conspicuous on salt-marshes, and should 

 be searched for in Britain. 



Rhizoclonium Kcraeri forma endozoiea forms green masses in the sponge 

 Halichondria, and probably occurs in England. 



Codium mucronatnm var. atlanticum. — This species is new to Europe. It 

 does not occur in the south of England, but is recorded in the present report 

 from south-west Scotland, Isle of Man, and the Orkney Islands, in addition to 

 the north, west, and south-west of Ireland. 



Stictgosiphon adriaticus. — Eare, and only obtained by dredging. It should 

 be found in quiet bays on the south coast of England. 



Acrothrix gracilis. — Probably very rare. Perhaps overlooked as 

 Mesogloia Grifjfithsiana. 



Fucus vesiculosus var. mtiscoides, var. nov. — This variety has never been 

 noted in England. It is probably confined to peaty shores. 



Spermothamnion Tumeri var. subvert icillatum. — I have not observed var. 

 subcerticillatum in England ; but it doubtless occurs in quiet bays on the south 

 coast, since it is known from France. In Clew Bay it is frequent throughout 

 spring and summer. 



Ptilothamnion lucifugum. — Caves are frequently explored by algologists ; 

 but this beautiful microscopic species has hitherto escaped detection. It 

 is allied to Ptilothamnion micropterum, which is only known from the 

 Canary Islands and Guethary (Basses Pyrenees). Probably a southern 

 species. 



Ceramium Borrgcsenii. — Doubtless common in England, but passed over 

 as C. decurrens. 



C. atlanticum. — This pretty and fairly well-marked species probably 

 occurs in England and Scotland. A few specimens only were found on 

 Clare Island. 



Lithophyllum incrustam, var. subdichotomum. — Identified correctly for the 

 first time by Dr. Lemoine, in the present report. Only known i n the 



