[ H 84 ]
LICHEN exanthematicus.
'Eruptive Lichen.
CRYPTOGAMIA Alga.
G en. Char. Male, fcattered warts.
Female, fmooth fhields or tubercles, in which the
feeds are imbedded.
S pec. Char. Cruft afh-coloured, fmooth. Shields
minute, concave, fleth-coloured, funk in little
hollows, and furrounded by a white lobed border.
Sy n . Lichen exanthematicus. Sm. Tr. of Linn. Soc.
v. 1. 81. t. 4. f 1. A char. Prod. 35* Dickf.
Cryp.fafc. 3. 14. With. v. 4. 22. Hull. 29X.
L. volvatus. Pillars. Dauph. v. 3. 998. t. 55.
Verrucaria claufa. Hoffm. Fl. Germ. 177.
T h i s curious little Lichen by its manner of excavating
ftones is clofely allied to L. immerfus, v. 3 . t. 193 . M. Villars
has publithed one by the name volvatus, which appears to
accord precifely with it, and we have Profeflbr Hoffman’s
authority for its being bis Verrucaria claufa.
Our name, which though pofterior to Hoffman’s has been
retained by Dr. Acharius, expreffes the peculiar appearance by
which this Lichen is at firft fight diftinguithable, refembling
fmall white puftules breaking from a grey cruft. The cruft is
thin, fmooth and uniform, clofely adhering to calcareous
rocks, of a pale grey or flate-colour. Each fhield is folitary,
minute, concave, fleth-coloured or waxy, with a border of its
own fubftance and colour, and is funk in a little cavity, hollowed
not only out of the cruft, but out of the ftone beneath,
the margin of which cavity is furrounded, and in an early ftate
clofed, by a thick inflexed lobed white border.------It appears
to be a very rare fpecies. The only Englith fpecimens we have
feen were found by the Rev. Mr. Harriman on the banks of
the Tees, Durham. Mr. Dickfon has obferved the fame in
Scotland. July J lSOd. Pu7>ltfh.ecl by Jh * Sownnby. .LonJo»