blong, rounded at the ends, straight or somewhat curved,
undivided or forked at one or both extremities ; their margin
convex, even or slightly wrinkled, and so indexed as
almost entirely to conceal, in our specimen, the disk, which
is represented more open in Chevallier’s figure.
The lirellae of this species considerably resemble those
of O. Persoonii,t. 2345, but the areolate crust distinguishes
it at once both from that plant and from O. saxatilis of Flore
Française, (O. saxicola of Acharius, Syn. Lich. p. 71.) from
which O. calcarea (Engl. Bot. 1790.) seems to differ but
slightly and unessentially. It is much to be doubted
whether O. Persoonii be more than an imperfect state of O.
lithyrga of Acharius (Syn. Lich. p. 72.), whether this again
be distinct from O. saxatilis, and whether the three ought
not to be regarded as states of O. notha of Acharius (Syn.
Lich. p. 76. O. notha and diaphora Engl. Bot. 1890 and
2280.) altered by growing on stone. This species we would
call O. varia; a name given to one of its numerous varieties
by Persoon, who first described it. O. tridens (3. arenaria,
(Syn. Lich. p. 79.) we believe to be merely O. lithyrga on
coarser stone. O. tridens «. may safely be referred, as a
variety, to O. varia. The O. Persoonii y. strepsodina of
Acharius, (Syn. Lich. p. 71.)4he original Lichen simplex
of Davies*, who afterwards joined with it a real state of
O. Persoonii, appears to be properly a Lecidea, with extremely
.irregular patellulæ. This is represented on slate
in Engl. Bot. t. 2152. The other specimen figured in that
plate seems distinct, and is Lecanora milvina (3. privigna of
Acharius (Syn. Lich. p. 15). W. B.
* Trans, of Linn. Soc. v. 2. p . 283. t. 28. ƒ. 2.