406 PKOCEEDINGS OF THE AMERICAN ACADEMY 



and contained by a proper exciple, clothed by or concrete with the thal- 

 lus surrounding it) is, however, though very variously conditioned, and 

 often in this or that respect obscurely expressed, (the interior exciple 

 being now scarcely distinguishable, and now the proper exciple, and 

 the thallus now so predominant as to give a lecanorine character to the 

 apothecium, and now without any other than an accidental relation to 

 the apothecium,) if I do not mistake, the typical structure of the genus ; 

 and recognizable even in the well-known species, common to the North- 

 ern hemisphere, cited above. 



Thelotrema platycarpdm, sp. nov. : thallo effuso tenui Insvigato 

 dein ruguloso pallido (subfuscescente) ; apotheciis raajusculis innatis 

 dilatatis subscutelliformibus, disco piano ca^sio-pruinato excipulo inte- 

 riori membranaceo viridulo inflexo cincto, exteriori reflexo substellatim 

 fisso. Spor« octonae, parvulae, leviter fuscescentes, oblongo-ellipsoideze, 

 tetrablastfe, diara. 24 - 3-plo longiores. Trunks, in the island of Cuba, 

 Mr. Wright. Tliallus thin and often obscure, but becoming interrupt- 

 edly thicker, and at length rugulose, and pale-brownish-cream-colored. 

 Apotliecia large, reaching a line and a half in diameter, innate, much 

 dilated ; the flat, thin, pale-fuscescent disk, which becomes blackish 

 above and delicately pruinate, bordered by the thin, obscurely greenish, 

 erose, inflexed margin of the interior exciple ; the exterior margin 

 splitting in a somewhat stellate manner into reflexed divisions. Spores 

 small, slightly fuscescent, oblong-ellipsoid, often a little narrowed to- 

 wards one end or dactyloid-ellipsoid, from diblastish (when a^ thin 

 dissepiment is observable) becoming finally and regularly tetrablastish, 

 the sporoblasts roundish. Paraphyses filiform, conglutinate. The near 

 afiinity of this elegant Thelotrema to T. lepadinum can scarcely be 

 denied, notwithstanding the marked divergence of its spores. 



Thelotrejia Santense, sp. nov. : thallo crassiusculo tenuissime 

 ruguloso excrescentias coralloideas proferente e glaucescente demum 

 cinerascente ; apotheciis majusculis innatis urceolato-scutelliformibus 

 dilatatis, apertura amplissima, disco piano nigro albo-pruinoso excipulo 

 exteriori incurvo lacero-crenato cincto, interiori indistincto. Sporae 

 octonge, fuscaB, ovoideo-ellipsoidcfe, demum oblongo-ellipsoideje, 4-5- 

 blastge, sporoblastis irregularibus subdivisis Ig- - 4-plo diam. longiores. 

 On trunks of elm {Ulmus Americana) in the low country of the Santee, 

 South Carolina, 3fr. Ravenel. In Southern Alabama, Mr. Beaumont. 

 Thallus at first appearing in thin, roundish, somewhat powdery patches, 

 but becoming a quarter of a line thick, with a very delicately uneven. 



