15 104 Proceedings of the Royal Irish Academy. 



with Gronronts description that it is here recorded under his name, though it 

 is possible that further work may show that it is a distinct species. In 

 St. Paul and Iceland it occurred in warm springs ; but it is well known that 

 many algae which usually grow in ordinary temperatures are also found in 

 such positions. 



Clare Island, Kinnacorra rocks, near high water. October. 1911. 



Lyngbya confervoides C. Ag. 

 Well known on the north coast of Frauce, but apparently not hitherto 

 recorded as British. It closely resembles L. aestuarii, and might almost be 

 regarded as a form of that species ; Gomont. however, keeps them distinct. 

 The Clew Bay specimens are rather slender, usually measuring 10-14/j diam. 

 The sheaths, even in old and empty filaments, remain quite hyaline. 



Louisburgh and Mulranny. September, 1911, in brackish pools; probably 

 common. 



Microcoleus chthonoplastes Thuiv 

 It is surprising that this well-known and cosmopolitan species should not 

 have been previously recorded for Ireland, where it forms, as elsewhere, a definite 

 though inconspicuous plant-association (see p. 63). Adams listed it in his 

 ' Synopsis " ('08), but excluded it in 1910 (p. 211), as no published record of 

 the plant could be found It is abundant in Clew Bay, and is doubtless 

 common in other parts of Ireland. I took several samples from the banks of 

 the river Bann in May, 1910. 



Calothrix aeruginea Thur. 

 Apparently new to Ireland. Recorded by Adams in his " Synopsis.'' but 

 removed in his second paper (10. p. 211 ). Epiphytic on various algae, espeeially 

 at Old Head. 



C. fusca Born, et Flah. 



A species usually regarded as being confined to fresh-water ; but found 

 in plenty on Wiizodoniuin riparium in brackish pools at Mulranny. It was 

 listed by Adams as an Irish fresh-water species. 



C. endophytica sp. nov. 1 (Plate 10, figs. 1-3). 

 Plants endophytic in the thallus-cavity of Enteromoi-pha sp., nearly black 

 in the mass. Filaments simple or rarely slightly branched, very short. 



1 C. fills intra thullos Enteromorphae entophYticis, brevis-siniis 70-130 p. altis, 7-10^ erassis. 

 aeruginosas ; vagina tenui, achroa, vel lutescente, sursum geiatinosa, diffluente : trichomatibus 

 7-8 n erassis. attenuatis : articulis diametro brevioribus vel subaequilongi? ; heteroeystis 1-2. 

 basilaribus. rare intercalaribiis. 



