16 146 Proceeding* of the Royal Irish Academy. 



Lithophyilum (Dermatolithon) pustulatum Fosl. 



Common on Clare Island, especially on Gigartina and Phyllophora rubens 

 in rock-pools, and near low-water mark. It was also found on Cludophora 

 rapcstris. 



Var. Corallinae Foslie (Melobesia Corallmae Crouan, Batt. Cat., p. 90). — 

 Common on Corallina officinalis in rock-pools on exposed shores. 



Var. Laminariae Foslie (M. Laminariae Crouan, Batt. Cat., p. 97).— Not 

 uncommon on stipes of Laminaria Cloiistoni. 



Distribution. — British Isles (common), Faeroes, Iceland, Norway, Sweden, 

 W. Baltic, Denmark, N. and W. France, Mediterranean, Adriatic, Morocco, 

 Canaries, Greenland, Atlantic coast of N. America. (Mass., Florida, Bermuda, 

 W. Indies), Pacific (California). 



L. (Dermatolithon) hapalidioides Fosl. 



Dredged in Clew Bay on several occasions, and probably not uncommon, 

 though often overlooked. The sub-littoral form is smooth, and very different 

 in appearance from the variety confinis. 



Var. confinis Foslie.— On Patella shells near low-water mark, not 

 uncommon. 



" La structure est la meme dans le type et la variete, et c'est pourquoi 

 Foslie (1909, p. 128) a reuni les deux especes L. (D.) hapalidioides et 

 D. confinis. Comme il le fait remarquer, le L. confinis correspondrait a la 

 forme squamidosa du L. Zenormandi ; on peut supposer que la var. type vit a 

 une certaine profondeur sur les coquilles et au concraire que la var. confinis vit 

 dans la limite des marees. La difference d'aspect resulterait d'une difference 

 dans les conditions de vie." (M. Lemoine.) 



Distribution. — British Isles, Faeroes, S. Norway, N. and W. France, 

 N. Spain, Algeria, S. France (last three localities var. confinis only). 



L. incrustans Philippi. 



L. incrustans is the common incrusting alga of pools and rocks on exposed 

 shores ; and, with the exception of Lithothamnium Lenoi'inandi, which forms a 

 belt above it, it is the only species normally occuring in the littoral region 

 (see p. 41). In the shallow waters of Clew Bay, a very smooth form in 

 addition to the ordinary is frequently found. 



Var. subdichotomum Heydr. — To this curious variety must the L. dentatum 

 of the west of Ireland be referred. The record is due to Foslie, who dredged 

 specimens in Roundstone Bay in 1899. He first regarded them as forms of 

 L. fasciculatum, but later referred them to L. dentatum. The latter is a 

 native of the Adriatic ; but though recorded from Naples and Tangier, its 



