deposited in the writer's herbarium, and a cotype may be found in the
State Herbarium.

This species is a coarser plant than _Buellia turgescens_ (Nyl.) Tuck.,
with much stronger, darker thallus and apothecia on the whole larger.




Rhizocarpon Ram. in Lam. & DC. Fl. Fr. ed. 3. 2: 365. 1805.

Thallus usually verrucose, areolate or subareolate, tending toward
squamulose conditions, better developed than in other members of the
family, scarcely ever showing granulate conditions, and never
disappearing entirely; apothecia also larger than in the other genera,
adnate to immersed, usually black, but rarely white-pruinose;
hypothecium usually dark brown; hymenium pale to light brown; spores
4-celled to muriform, and pale to brown, various conditions of septation
and coloration sometimes appearing in the same hymenium.


KEY TO THE SPECIES OF RHIZOCARPON

On bark 2. R. _alboatrum_
On rocks.
Spores smaller and 4-celled 1. R. _vernicomoideum_
Spores larger and becoming muriform 3. R. _petraeum_


1. Rhizocarpon vernicomoideum sp. nov.