Knowles — The Maritime and Marine Lichens of Howth. 139 



pore which measures 15-20 ft in diam., peritheoial wall dimidiate; ascus 

 elliptical, 20-25 /^ x 10-12 fi ; spores eight in the ascus, simple, rod-like, 

 oblong-elongate or slightly curved, 15-18 ;u x 2-4 /i, regularly or 

 irregularly grouped in the ascus. 



Habitat. — Limestone rock inside neap-range at Balscadden Bay, 

 more abundant near low- water mark. It is associated with V. microspora, 

 Arthopyrenia Uloralis and A. foveolata. 



In Sandstede's paper on the lichens of the German North Sea islands 

 (25, p. 16) Bouley de Lesdain has described a new species — Verrucaria 

 Sandstedei — which in the effuse thallus and the size of the ascus is 

 almost identical with Verrucaria Lor rain- Smithii. The two species, 

 however, are separated by the character and size of the perithecia, 

 which in V. Sandstedei are immersed, sometimes confluent, and measure 

 l*5-2mm., whilst in V. Lorrain- Smithii they are prominent and excessively 

 minute, measuring only about 175^ in diameter. The spores, too, of 

 V. Sandstedei are both longer and broader than those of V. Lorrain- 

 Smithii, the former measuring 16-21 ^u x 3-5'5 (rarius 4)^, and the 

 latter 15-18^ x2-4^. 

 Thelidium cataractarum Mudd. — On sliady cliffs with a north aspect, 

 Balscadden. The Howth plant differs in some points from Mudd's 

 specimens in the British Museum. The thallus is lighter in colour and 

 more farinaceous-tartareous, and the asci are more elongate. The spores 

 also, though agreeing in colour, size and septatiou, are very distinctively 

 guttulate — a feature not noticed in those of Mudd's specimens. These 

 differences are probably due to the maritime habitat, and do not seem to 

 me to be sufficient to justify the creation of a new species. 

 Aerocordia gemmata Koerb. — On Blackthorns, Earlscliffe ; rare. 



tArthopyrenia epidermidis Mudd. — On Blackthorns, Earlscliffe ; rare. 



fA. punctiformis Arn. — On Blackthorns, Barlschffe ; rare. 



fA. litoralis A. L. Sm. — Found only on limestone rocks inside neap-range, 

 Balscadden Bay, and on barnacles. Old Boat-house. 



The size of the perithecia in the Howth specimens varies a good deal, 

 some of the largest measuring 0'4-0'5 mm. in diameter ; the asci are 

 cylindrical, and also variable in size, measuring 80-150 /xx 15 ju,; the 

 spore measurements are 15-22 fx x 5-7 ju, and are larger than those given 

 iu the " Monograph of British Lichens." 



tA. foveolata A. L. Sm. — On barnacle shells all round the coast, and on lime- 

 stone rocks between tide-marks, Balscadden Bay, associated with 

 A. litoralis ; very abundant. 



fA. leptotera A. L. Sm — On Broad Strand and Ireland's Eye, on rocks 



