Knowles — The Maritime and Marine Lichens of Howth. Ill 



band just above a copious growth of Enteromorpha. In several places 

 V. pivmiiiuhi var. viridans v?as found associated, and occasional small patches 

 of V. maura occurred here and there. The thalli of the Verruearias were, 

 however, so obscured by a copious growth of Gloeocapsa and other unicellular 

 algae that the species were not easily recognized. 



The Verriicaria maura belt forms a transition zone between the maritime 

 and the truly marine lichens, and constitutes Weddell's semi-marine group. 

 It has been referred to by various lichenologists ; Nylander describes it as 

 forming a definite zone on the shores of Pornic limited by tlie two Li chinas ; 

 Weddell defines its habitat on the coast of Brittany as rocks that are 

 submerged or wet by the waves at high tide. Warming records it as 

 being widespread along Arctic and northern seas, and says tliat on Swedish 

 and Danish coasts it occurs on rocks that are " very frequently wet," and he 

 quotes Beck von Mannegetta's (15) account of the "often pitch-black crusts" 

 of V. maura that colonize the wet rocks along the Adriatic. For tlie British 

 coasts, A. D. Cotton (3, p. 20) describes it as forming, on the exposed coasts of 

 the Clare Island Survey Area, " a band a short distance above the Pelvetia 

 zone"; and Miss Lorrain Smith (28, p. 3) describes "the rocks bordering 

 the sea," and the " great cliffs " of the north-west coast of Clare Island as 

 " black with an unbroken growth of Verntcaria maura." 



On the exposed coasts of the West of Ireland Verrucaria maura often 

 grows at great heights above sea-level. On the small uninhabited High 

 Island off tlie coast of County Q-alway, where the seas are severe and the 

 island in winter storms is swept from end to end by the spray, V. maura and 

 Lichina confinis form a zone along the top of the cliffs in places more 

 than 200 feet above the ocean. 



(5) The Belt of Marine Verruearias. 



This belt comprises all the marine encrusting lichens, those tliat are 

 submerged by the incoming tide for a longer or shorter period each day. 

 It lies mainly inside neap range, but on low flat shores, where the tides rise 

 and fall gently, straggling colonies are found as far down as the lowest 

 spriug-tide level. The lichens of this belt form a more or less continuous 

 covering on the rocks of the upper part of the beach, but the growth becomes 

 meagre and spotty nearer low water. The dominant species are Verrucaria 

 microspora, V. striatulu, and V. mucosa ; and Arthopyrenia halodytes, which has 

 already been mentioned in connexion with the Verrucaria maura belt, is also 

 abundant in the upper part of this belt. Besides tliese, three other species, 

 Arthopyrenia halizoa, A. leptotera, and A. marina, are sometimes present, but 



SCIENT. PKOO. E.D.S., VOL. XIV. NO. VI. E 



