Clare Island Survey — Marine Algae. 15 139 



P. subulifera Harv. 

 This rather rare species is apparently frequent in the west of Ireland, 

 being found abundantly in Clew Bay, Achill Sound, and also in Roundstone 

 Bay. Harvey notes its frequency on the Lithothamnium banks at Round- 

 stone ; and in September, 1911, it was the dominant species. It was also 

 dredged on similar ground in Clew Bay, and appears to be one of the 

 Florideae which can withstand considerable insolation in shallow water. 



Dasya arbuscula Ag. 

 The frequency with which this plant is met with in Ireland at once strikes 

 the collector as a great contrast to the south of England, where, though found 

 from Laud's End to the Isle of Wight, it is always rare. Harvey (Phyc. Brit.) 

 notes its abundance at Bantry Bay, and on Clare Island it may be regarded 

 as one of the most frequent and constant of the miscellaneous collection of 

 Redweeds that occur near low-water mark on moderately exposed rocky 

 shores (e.g. Kinnacorra). At certain seasons also it is washed ashore in 

 plenty (July, August ?). 



Ptilothamnion lucifugum sp. nov. 1 (Plate IX). 



Plants gregarious, minute, 1-1-5 cm. high. Fronds decumbent at the 

 base, then erect, producing branches and pinnae irregularly. Branches 

 3-6 mm. long, irregularly beset with pinnae ; cells, 35-50 n wide, by 3-4 times 

 as long. Pinnae short, 2-3 mm. long, opposite, but more often irregular, 

 usually naked below, but bearing above regularly opposite forked pinnulae ; 

 cells 25-30 /n wide by li-2 times as long. Pinnulae bifid through the 

 production of a lateral branch on the under side of the lowermost cell, rarely 

 simple, very rarely trifid; cells 15-20 ji wide by l|-2 times as long. Decumbent 

 portion of the frond irregularly attached to the substratum by rhizoidal 

 pinnae, which occasionally terminate in a discoid expansion. Tetraspores 

 and cystocarps unknown. Antheridia borne on the terminal cells of the 

 pinnulae. 



Habitat. — Attached to rocks in shallow 'pools in a dark cave, Portlea, 

 Clare Island, August, 1911. 



Closely allied to P. micropterum (Mont.) Bornet, but distinguished by its 

 irregular branching, larger size, and peculiar habitat. 



The present species was found as a dense mossy covering on the bottom 



1 Frondes caespitosae, 1-1*5 cm. altae, ramis priinariis repentibus secundariis erectis. Pinnae 

 2-3 mm. longae, pinnulis omnibus furcatis aut rare simplicibus. Articuli ramorum 3— tplo 

 pinnamm l-2plo diametro longiores. Sporangia et cystocarpia ignota. Antheridia in articulo 

 terminali pinnularum eToluta. Hab. In spelunca. 



Species P. microptero proxima Bed frondibus majoribua inegularibus differt. 



S2 



