KnoWles — The Maritime and Marine Lichens of Howth. 99 



(1) Orustaceous lichens occur throughout the belt, but are most abundant 

 in the lower part amongst the Ramalina scopulorum growths. 



(2) Some species are peculiar in the upper part of the belt. Others are 

 only found in the lower part of it. 



(3) Some species are more abundant in shade and others in sunny 

 aspects. 



Of tliose that occur throughout the whole belt, Buellia canescens, B. 

 ryssolea, B. spuria, B. coUudens, B. myriocarpa, Lecanora atra, L. subfusca var. 

 campestris, L. ferruginea \a.v. fediva, L. smavagdula, L. mnjilexyax. strepsodina, 

 and Opegrirpha calcarea are some of the more frequent species. 



Tlie Buellias, as a whole, are most often met with on dry, sunny rocks; but 

 some species prefer shade and shelter. 



Buellia canescens likes shade, and is often seen in very deep shade growing 

 either round the attachments of Ramaliuas in the centre of dense growths or 

 covering the under-surface of slightly overhanging rocks, the tops of which 

 are clothed with Kamalinas. In such very shady situations as these the 

 thallus is always greenish in colour. This species was more frequently seen 

 on the eastern and northern coasts ; on the south and south-west coasts it grew 

 most often on rocks with easterly or northerly aspects. On the Howth shores 

 Buellia canescens is widespread, but always barren. 



Buellia ryssolea is very common amongst the Ramaliuas, and often covers 

 large areas of rock outside the Ramalina growths with its grey map-like 

 thallus. It likes sloping shady rocks ; and on the Howth coasts it is usually 

 to be seen on those with an easterly aspect. It avoids the pure quartz rock. 

 In many places growths of this lichen where they encountered quartz veins 

 stopped short on either side, leaving the quartz uncovered as a conspicuous 

 white band in the middle. 



Lecanora parella is a very scarce species. It only occurs here and there 

 on the Broad Strand on the higher parts of the beach, and at one or two 

 places along the south-west coast. It was not seen on the cliffs, and seems 

 to be absent from the eastern and northern coasts. The growths were most 

 usual on rocks with a westerly slope, and among the Ramalina scopulorum 

 bristles, but were nowhere vigorous. The scarcity of tliis lichen along the 

 Howth shores is very remarkable, but seems to be chiefly due to the absence 

 of high rocks and boulders on the shore above the spray-zoue. Lecanora 

 parella is abundant along the west coast of Ireland, being one of the dominant 

 lichens on Clare Island (28), and on the coasts of N. Mayo and N. Galway, 

 where it covers the rocks and walls at a little distance from the sea with a 

 continuous creamy growth. 



Opegraplw calcarea. — This species is extremely abundant on the grits 



