fiev. W. A. Leighton on the British GraphMese. 93 



the inflexed mai'gins supporting the sides of a lamina proligera, 

 whose upper surface was covered in the centre with the thick 

 central portion^ the base being naked and resting on the rock. 

 The lamina proligera was pale andf hyaline, consisting of para- 

 physes, amongst which were asci of an obovate-elongated or 

 clavate shape filled with minute granular matter. 



Schleicher's specimen ! of 0. saxicola, Ach., in herb. Borrer, 

 seemed referable to this species, see p. 90 ante. 



Distinguished from O. saa;atilis by the shape of the lirellse and 

 sporidia ; from O. Chevallieri by the form of the lirellse ; from 

 O. tesserata and 0. cerebrina by the thallus and sporidia. 



Plate V, fig. 5. a. Vertical section of thallus and lirella ; b, sporidia. 



6. 0. saxigena, Tayl. Lirellse linear, linear-oblong, oblong 

 or ovate, deformed, obtuse at the extremities, chiefly simple and 

 straight, dark brown ; sporidia eight in asci, nan'ow, linear- 

 oblong, rounded at each extremity, 3-septate, pale yellow. 



Opegrapha saxigena, Tayl. Fl. Hib. pt. 2. 259. 



Dunkerron ! Dr. Taylor in herb. Borrer. 



Thallus moderately thick, crustaceous, indeterminate, irregu- 

 larly cracked, of a dirty rusty-brown coloui* in the older portions 

 where the crust is thinner, in the younger and thicker portions 

 and about the hrellse, of a scaly, crumbling, leprose, yellow ap- 

 pearance. LirellcE loosely congregated in groups, very various 

 in shape, round or punctiform, oblong, hnear-oblong, lineai', 

 ovate, subtriquetrous, modified by branching into an irregular, 

 oblong, triquetrous form, generally simple, straightish or slightly 

 cm'ved and waved, very obtuse at the extremities, dark brown, 

 smooth, somewhat shining, the margins incurved, tumid and 

 round, slightly rugged or broken. Disk generally narrow, 

 straightish, though varying in width and direction according to 

 the form of the lirella, yet not widely open and expanded, the 

 margins always rounded and incm'ved, tumid, not sharp-edged 

 as in O. rupestris. The sporidia are sometimes broader at one 

 end than the other, and so approaching a subclavate form. 



So closely allied to 0. rupestris, that, notwithstanding the 

 above differences, we shall perhaps do well in hesitating to pro- 

 nounce it decidedly distinct from that species. 



A specimen ! in Mr. Borrer's herbarium from Dr. Taylor, 

 labelled by him " Opegrapha saxigena, Fl. Hib., var. trochodes, 

 (new variety), Carig Mountain, Co. Kerry," proved on exami- 

 nation to be the deformed patellulse of some Lecidea. (See PI. Y, 

 fig. 8 a & b). 



Plate V. fig. ?• a, Vertical section of thallus and Urella ; b, sporidia. 



