2727
LECANORA ftmnaria.
White mealy-crusted, Lecanora.
CRYPTOGAMIA Lichenes.
Gen. Char. Scutellce sessile, with a margin of the
same substance as the thallus.
Spec. Char. Crust indeterminate, soft, mealy, pulvi-
nulate, white. Scutellas slightly elevated; margin
mealy, uneven; disk livid-brown, pale within.
O n old rails, not uncommon in Sussex, but rarely bearing
scutellae, which have been observed at Henfield and at
Hurstpierpoint.
Thallus composed of minute mealy particles, with a filmy
or slightly tartareous substratum observable, under favourable
circumstances, beneath them, from which they burst, and
which they usually soon conceal, becoming confluent in small,
roundish, pulvinate masses, and by degrees forming an uneven
crust, varying in thickness, and irregular in outline,
and often spreading to considerable extent: its colour
when perfect, white, with the faintest possible tinge of
green, in long-kept specimens greyish. Scutell®, when
found at all, usually numerous and often clustered but
small and inconspicuous ; their outline mostly wavy, with
a thickish indexed margin from the crust, which in old
shields is sometimes so depressed as to leave the edges of
the disk bare, and to render the generic character ambiguous
: disk at length convex; its hue a livid brown varying
in intenseness, the internal substance paler § when dry,
nearly black externally and almost white within.