OF ARTS AND SCIENCES. 405 



THELOTREMA, Ach. Nyl. Some of the species differ no little 

 in aspect from the well-defined T. lepadinum, Ach. ; and Fee (Ess., 

 Suppl. p. 88) and others have proposed to separate the latter generi- 

 cally. But though the distinction of the excipular margins is often 

 obscure in the tropical species, and these vary also very considerably 

 in the figure, coloring, and internal differentiation of the spores, which 

 are commonly smaller and more simple than those of T. lepadinum ; 

 it appears to me that the Cuba lichens referable here, in accordance 

 with Dr. Nylander's limitation of the genus (Enum. Gen. p. 117), or, at 

 least, those of which the descriptions follow, are none of them properly 

 separable from it, or from T. lepadinum. And this view is, if I mis- 

 take not, in full accordance with Eschweiler's laborious observations 

 (Lich. Bras. p. 173). 



Thelotkema lepadodes, sp. nov. : thallo effuso tenuissime mem- 

 branaceo diffracto cinereo-albicante ; apotheciis submediocribus super- 

 ficialibus e conoideo tympaniformibus, apertura ampla excipulo exteri- 

 ori urceolato albido (fuscescente) thallo vestito discum nigricantem 

 albo-pruinosum excipulo interiox'i discreto membranaceo albo margina- 

 tum margine demum subrecurvo integro cingente. Sporae suboctonje in 

 thecis clavatis, majusculae, fuscescentes, oblongge, serialiter polyblastse 

 (ser. transversis 1 6 - 24, longitudinalibus in medio 4), diam. 3 - 5-plo 

 longiores. On trunks, Filanthropia, island of Cuba, Mr. Wright. 

 Thallus membranaceous, much and finely broken, or scurfy, ashy- 

 whitq. Apothecia a third of a line in diameter, superficial ; the younger 

 ones exactly truncate-conoidal, but the oldest more cylindraceous or 

 drum-shaped, with an ample aperture ; a proper urceolate exciple, 

 more or less clothed by the thallus, but occasionally denuded and fusces- 

 cent above, bordering with an entire, finally a little recurved margin a 

 blackening white-pruinose disk, which is itself loosely edged by a 

 white, membranaceous, inflexed, sometimes obscure interior exciple. 

 Spores large, fuscescent, oblong, serially polyblastish. Paraphyses fili- 

 form, flexuous. Appearing at first sight to differ from T. lepadinum, 

 mainly in the more erect, finally recurved outer margin, and the colored 

 and otherwise somewhat discrepant spores ; but the real difference is, 

 if we accept the common definitions of T. lepadinum, much greater ; the 

 so-called thalline, outer exciple of the latter being represented in the 

 present by what is plainly a proper exciple ; that is, one not formed from 

 the thallus, though more or less covered by it This structure (that is to 

 say, a sporigerous disk, veiled by a more or less distinct interior exciple, 



