Knowles — The Maritime and Marine Lichens of Howth. 135 



been able to see specimens of this species for comparison, but the Howth 

 plant agrees so well witli the description of B. invpresmla in vol. II of the 

 " Monograph of British Lichens," that I have little hesitation in referring 

 it to this species. The apothecia are small, circumscribed, and often 

 three or more together. The spores measure 1 2-14 ju x 8-9 ju, and are 

 slightly constricted at the septum, which is rather thick. Tlie hypo- 

 thecium is pale, brownish-yellow, the paraphyses are indistinct, and the 

 hymenial gelatine turns bluish with iodiue. 



The only previous records are from hilly districts in Wales. 

 tB. atrata Mudd. — East coast ; frequent. 



tB. coUudens Tuckerm. — On rocks all round the coast ; common. 

 fB. confervoides Krempelh. — On slaty rocks in dry situations, and often 

 associated with L. mnplex f. sirepsodina ; common. 

 B. atroalba Th. Fr. — Only noted on dry rocks near the Needles, but it 

 is probably frequent. 

 tLeciographa parasitica Massal. — On the thallus of Physcia parietina, about 

 high-water mark, Broad Strand. The spores of the Howth specimens 

 are very occasionally four-septate ; but in all otlier respects tlie plant 

 agrees with the descriptions of this species. 

 *L. glaucomaria A. L. Sm. — On the thallus of Lecanora glaucoma at White 

 Water Brook, and at other places on the east coast ; rare. 

 Rhizocarpon alboatrum Th. Fr. — A very common species on rocks about 

 high-water mark, associated with Placodium lohulatum and Lecanora 

 prosechoides (see page 101). 



fvar. vemistum A. L. Sm. — Forms pure colonies on quartzite rocks 

 splashed by the sea at high tide, near the Martello Tower, 

 Sutton, and at various other places on the south-west coast, 

 fvar. epipolia A. L. Sm. — Frequent on rocks and stones at the base 

 of the earth-banks. Broad Straud ; also on tlie limestones at 

 Balscadden Bay. 

 Rh. geographicum DC. — On rocks from sea-level to the top of the highest 

 cliffs on the east coast ; less general at low levels on the south and 

 south-west coasts. It is usually associated with Lecanora glaucoma, and 

 is frequently infested with Muellerella pohjspora Hepp. 

 Rh. petraeum Massal. — Occasionally on schistose and quartzite rocks and 

 stones on the shore above high-water mark, Broad Straud ; frequent on 

 the east coast. 



fvar. excentricum A. L. Sm. — On limestone, Balscadden ; rare. 

 fBh. confervoides DC— On quartzites, frequent round the coast. 



SCIENT. PKOC. K.D.S., VOL. XIV., NO. VI. U 



