General Appearance:  ( all the species ) Whitish to pale gray patches on the bark consisting of a paint-like film inseparable from the outer bark; the patches usually 0.5-3 cm ( 1/8 - 1/4 in ) across.  Thallus: ( all three species )  Thallus crustose, the lower surface embedded in the bark. Upper surface whitish, dull, smooth or divided into irregular polygons which often appear outlined in black.  (Use a hand lens)

 
 

Apothecia: ( all three species ) Apothecia present, disk-shaped, 0.3 -1.0 rnm. (.01- .04 in) wide, with a     whitish thalline margin.  Lecanora carpinea: Apothecial disk fla.t or slightly convex, pale pinkish when dry and similarly      colored when wet; thalline margin often inditinct on older apothecia and present as minute lumps around the margin of younger ones.  (Use a hand lens) Apothecia clustered close together and appearing as polygons. Lecanora confusa: Apothecial disk flat or slightly concave, pale olive-green when dry, similarly colored when wet; thalline margin easily seen but thinner than in L. pacifica. Lecanora pacifica:  Apothecial disc flat or slightly concave, blackish to dark olive brown when dry, lighter-colored, olive to yellow-green when wet; thalline margin thick. Soredia:  ( all species )  Lacking. Isidia:  ( all species )  Lacking. Comments:  In the genus Lecanora, species are distinguished by their apothecia which are almost always present on their whitish to grayish crustose, paint-like thalli.  Lepraria species have a similar thallus but it is colored blue-green or yellow, and always lacks apothecia.  Rinodina species resemble Lecanora species but have a blackish thallus.