102 Scientific Proceedings, Royal Dublin Society. 



In Slimmer the colour of these lichens is so brilliant that the belt is easily- 

 recognized from a considerable distance. It may be very distinctly traced 

 on the cliffs near the Needles and on the rocks of the Broad Strand as one 

 walks along the top of the cliffs from Drumleck Point towards Baily. On 

 the east coast it may also be seen on the western and southern slopes of 

 the lower cliffs. In winter or during long spells of wet weather it assumes 

 a greenish-yellow colour and is not quite so conspicuous. 



The most abundant species and those which give the characteristic 

 orange colour to the belt are : — 



Physcia parietina. Placodium decipiens. 



Placodium murorum. lobulatum. 



tegularis. 



In addition to these bright-coloured lichens several others less noticeable 

 on account of their grey or nondescript colour, also form important elements 

 of the belt. The chief of these are : — 



Lecanora prosechoides. Biatorina lenticularis. 



umbrina. Rinodina exigua var. demissa. 



Opegrapha calcarea./! heteromorpha. 



Ehizoearpon alboatrum. 



Of the species in the first list Physcia parietina is more yellowish in hue, 

 and usually forms a distinct colour band above the Placodiums. The effigu- 

 rate thallus of the rarer Placodium murorum is more frequently seen in the 

 middle of the belt, while the more crustaoeous P. lobulatum comes lowest 

 on the shore. This arrangement is well seen on several parts of the Broad 

 Strand. Here on the stones and low shore-rocks that lie just above the 

 ordinary high-tide level, Placodium lohulatum grows abundantly, covering the 

 rocks with a continuous sheet of brilliant colour. In some places it extends 

 down the shore into the Pehetia cananiculatus belt. At this level, however, 

 the Placodium does not form a continuous sheet, but variegates with greenish- 

 orange spots the black crust of Verrucaria maura. Placodium murorum and 

 Physcia parietina are also occasionally found in the Pelvetia belt, but the 

 normal position of these two species is at a higher level, where they usually 

 form two consecutive zones in the order stated from below upwards. All 

 three lichens are frequently submerged at high spring-tide. 



On the sheltered sunny beach of the bay below Earlscliffe, the waves roll 

 gently over the rocks with scarcely any splash except in the roughest weather. 

 But a little further to the east higher and bolder rocks occur standing rather 

 more out to sea. As one approaches these rocks the sequence of the three 

 lichens is broken ; Physcia parietina has moved up under tiie Ramalinas for 



