222 PROCEEDINGS OF THE AMERICAN ACADEBIY 



19. P. incurva, Fr. Th. cartilagineous-membranaceous, stellate-im- 

 bricate,'globuliferous, greenish-straw-colored (and ochroleucous) ; black 

 and fibrillose on the under side ; lacinise very narrow, multifid, subte- 

 rete, recurved at the apices ; apoth. rufous-fuscous, subentire. Fr. 

 Lichenogr. p. 70. P. reairva, Ach. 



Rocks in mountainous districts (subalpine, and descending). White 

 Mountains ; fertile. 



20. P. amhigua, Ach. Th, membranaceous, orbicular, stellate-im- 

 bricate, farinose-sorediiferous, greenish-straw-colored (and ochroleu- 

 cous) ; black and fibrillose on the under side ; lacinise plane, linear, 

 appressed, multifid ; apoth. adnate, rufous-fuscous, very entire. Fr. 

 Lichenogr. p. 11. 



Trunks and dead wood in mountainous districts, fertile ; and on 

 rocks, infertile ; White Mountains. Northward to Arctic America, 

 Rich. 



21. P. centrifuga, Ach. Th. submembranaceous, suborbicular, 

 greenish-straw-colored (and ochroleucous) ; white and fibrillose on the 

 under side (the crust-like centre often falling away, and leaving a con- 

 centrically disposed circumference) ; lacinise linear, concrete, convex, 

 rugose; apoth. rufous-fuscous, margin subentire. Fr.! Lichenogr. p. 11. 



Rocks (subalpine and descending) in mountainous districts, fertile ; 

 New England. New York, Torrey. Pennsylvania, Muhl. North- 

 ward to Newfoundland, Herl. Banks ! Pylaie. An ochroleucous, 

 black-punctate, not concentrically disposed state is P. Halseyana, 

 Tuckerm. Lich. N. E, 1. c. It occurs in the Notch of the White 

 Mountains. 



Series 4. C itr in m , Fr. 



22. P. parietina, Fr. Th. foliaceous or squamulose, imbricate, mem- 

 branaceous, sublobate, yellow ; paler and obsoletely fibrillose on the un- 

 der side ; apothecia with elevated margins, very entire. Fr. Lichenogr. p. 

 12. — a. (foliacea), Fr. ; th. foliaceous, from greenish becoming bright 

 yellow; lobes explanate, appressed. P. parietdna, Ach. — /5. aureola^ 

 Fr. ; th. foliaceous, somewhat zoned and subcentrifugal, dark-golden- 

 yellow ; lobes concrete, plicate-ramose. P. aureola, Ach. — y. rutilans, 

 Fr. ; th. foliaceous-subcrustaceous, imbricate-complicate, irregularly la- 

 ciniate. P. rutilans, Ach. — 8. laciniosa, Duf. ; th. naked, lacerate-dis- 

 sected, squamulose; lacinise ascending, naked. — e. polycarpa, Fr. ; 

 th. smaller, conglomerate ; the lobes complicated, and covered with the 



