the name of Lecanora tribacia, and his spec. char, is adopted
for Sqitamaria tribacia in the Brit. FI.
Thallus radiant and roundish in young distinct plants ;
but mostly found in large, irregular, crowded imbricated
patches. Substance thin, green within ; surface to the naked
eye even, under a glass minutely granulated, grey with
a pale tinge of green when wet, grey-white or somewhat
lead-coloured, especially at the edges when dry ; underside
white, brownish in the central parts, attached by short pale
fibres, which are usually not very numerous. Segments
much divided, imbricated and entangled, variously sinua-
ted; flat or slightly convex where free at the edges of the
patch ; elsewhere for the most part ascending from mutual
pressure ; the ultimate lobes rounded, with decurved, minutely
jagged, crenulate or granulated edges. Sometimes
the edges are raised, and, producing mealy granules on the
underside, assume, although not hollow, an appearance approaching
to that common in P . tenella. There are no soredia
on the surface. Scutellæ not larger than rape-seed, but
little elevated, orbicular; the margin rounded, and, on
Mr. Salwey’s specimen, mostly entire, but in one instance
showing a tendency to become leafy ; disk black.
Nearly allied to P. cæsia, t. 1052; but, besides the peculiarity
of the edges, the segments are broader and more
imbricated, and the globular soredia are wanting, nor is
there anything like the copious superficial granulations of
another related Lichen, P . Clementi, t. 1779. The shields
have not the blueish surface observable in the two species
last-mentioned, and in P. stellaris and others of the same
section ; but we have seen too little of them to answer for
the constancy of this différence.—W . B.