120. Psora] 33. LECIDEACEAE 213 



Thallus composed of minute to small, round, adnate, crenate and lobulate, 

 brownish gray to ashy white, often imbricate squamules, or the squamules run 

 together into a rough, warty, irregular crust, on a black hypothallus; apothecia 

 small to middle-sized, 0.4-1 mm. across, adnate, sometimes confluent, the disk 

 fiat to convex, dark reddish brown to black, the exciple thin, darker, and soon 

 disappearing; hypothecium hyaline; spores ovoid-ellipsoid, 10-18X5-8 /a. 



On soil, Vermont, New Hampshire, Colorado, and Washington. 



2. Psora luridella (Tuck.) Fink n. comb. 



Lecidea luridella Tuck., Proc. Am. Acad. 5:418. 1862. Biatora luridella Tuck. 



Thallus composed of small, rather thick, closely adnate, round, finally crenate- 

 lobed, subimbricate, dull brownish yellow to dark red squamules, the margins and 

 rarely whole squamules whitish pruinose; white below; apothecia minute to small, 

 0.4-0.8 mm. across, adnate, the disk convex, dark brown to black, the exciple thin 

 and disappearing; hypothecium hyaline; spores ovoid-ellipsoid, 7-12X4-6//.. 



On soil, Colorado, New Mexico, California, and Washington, usually in moun- 

 tains. 



3. Psora rufonigra (Tuck.) Schneid., Guide Study Lich. 119. 1898. 



Biatora rufonigra Tuck., Proc. Am. Acad. 1:250. 1848. Lecidea rufonigra 

 (Tuck.) Nyl. 



Thallus composed of small, smooth, rather thick, concave, irregular and lobed, 

 commonly ascendant, more or less imbricated, brownish or greenish to blackish 

 squamules; commonly darker below and clothed with dark rhizoids; apothecia 

 small to middle-sized, 0.3-0.9 mm. across, adnate, the disk flat to convex, dark 

 brownish to black, the exciple colored like the disk, soon disappearing; hypothe- 

 cium hyaline; spores oblong-ellipsoid, 8-15 X 5-7 /x. 



On rocks, throughout the United States. 



4. Psora Petri (Tuck.) Fink n. comb. 



Biatora Petri Tuck., Proc. Am. Acad. 12:179. 1877. Lecidea Petri (Tuck.) 

 Zahlbr. 



Thallus composed of small to middle-sized, rough, round to oblong or irregular, 

 concave, undulately lobed, loosely imbricated, pale greenish gray to brownish 

 squamules, on a thin brownish hypothallus; apothecia middle-sized to large, 0.6- 

 2.5 mm. across, sessile to somewhat elevated, the disk flat, reddish to blackish, the 

 exciple thick, dark brown, flexuous and finally disappearing; hypothecium hyaline 

 to yellowish; hymenium hyaline to bluish black toward the top; spores ovoid- 

 ellipsoid, 9-11 X4-5/1. 



On mosses of calcareous areas, Alabama and Tennessee. 



5. Psora scotopholis (Tuck.) Fink n. comb. 



Biatora scotopholis Tuck., Lich. Calif. 24. 1866. Lecidea scotopholis (Tuck.) 

 Herre. 



Thallus composed of minute, thin, round, convex, glistening, blackish chestnut- 

 brown, often areolate squamules upon a black fringing hypothallus, the squamules 

 becoming elevated at the crenately lobed, crowded, and subimbricated margins; 

 apothecia middle-sized, 0.5-1 mm. across, adnate-sessile, the disk flat to convex, 

 reddish to dull black, the exciple thick, brownish black, becoming crenulate and 

 finally disappearing; hypothecium hyaline to brownish; spores ellipsoid, 7-12 X 

 3—5 fi. 



On rocks, California and Oregon. 



6. Psora Russellii (Tuck.) Schneid., Gen. Lich. 141. pi. 25. 1897. 



Biatora Russellii Tuck., Lich. Calif. 23. 1866. Lecidea Russellii Tuck. Biatora 



Russellii f. dealbata Tuck. 

 Thallus composed of small to middle-sized, rather thick, round or irregular, 

 more or less lobed, dull or reddish brown or finally whitish, sometimes reticulately 



