Clare Island Survey — Marine Algae. 15 123 



plant is usually smaller in all its parts, especially in the basal thallus. It 

 is, moreover, apparently to be found throughout the entire year, whereas 

 A. foecundus has a much shorter season. 



Ralfsia verrucosa Aresch. 

 Very common in many parts of our district. In shallow rock-pools on 

 the upper part of the shore it forms large spreading sheets, which may com- 

 pletely cover the bottom. At a lower level it usually occurs on bare rock. 

 Occasionally it was dredged from the shallow sub-littoral region. 



Lithe-derma faticens Aresch. 



It is disappointing not to be able to record this plant (a species supposed 

 to be widely distributed) with certainty for Ireland. Many Lithoderma- 

 like plants were dredged in Clew Bay during summer, but these, as was 

 expected, proved sterile. The special February trip provided a large number 

 of specimens, some of which Dr. Kuckuck informs me can be doubtfully 

 referred to Lithoderma. A few of the specimens obtained proved to be Petro- 

 derma maadifornie, which shows the risk of naming these plants from 

 imperfect material. 



Petroderma maculiforme Kuck. 



A few specimens of this species (which is an addition to the British flora) 

 were detected by Dr. Kuckuck amongst material dredged in Clew Bay 

 during February. The plant resembles Lithoderma very closely in external 

 appearance, but differs in the character of sporangia and other minor points. 



Spermatochnus paradoxus Kiitz. 

 Extremely abundant during July and August in the low-littoral of Achill 

 Sound, Bellacragher Bay, and in the inner part of Clew Bay. It is epiphytic 

 on many of the larger algae, and forms large tangled masses a yard or more 

 square : in some of the channels of Achill Sound it is for a time com- 

 pletely dominant. In contrast to the present species Stilophora rhizode-s is 

 comparatively rare. 



Mesogloia lanosa Cm. 



Several plants of this rare alga were dredged near the lighthouse in Clew 

 Bay during July, 1909. Its season is probably short, as it was not met with 

 in any subsequent dredgings. 



M. Griffithsiana Grev. 

 It was very satisfactory to find during the last days of the field-work the 

 true M. Griffiihsiania, since the specimens collected as this species in 1910 



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