OF ARTS AND SCIENCES. 417 



the genus, Dr. Nylander has described another ( C. complexum, Lich. 

 Exot. 1. c. p. 222), with shorter, coarser, tomentose filaments, larger 

 apothecia, and diblastish spores, which (first collected in Bolivia by 

 "Weddell, and since in Venezuela by 3fr. Fendler) has not yet occurred 

 in the Cuba collections. The apothecia of Ccenogonium especially 

 resemble those of Gyalecta (or Lecidea) lutea ; as if the former were, 

 in fact, to use Fries's words (S. O. V. p. 301), "Biatora in thallo 

 Byssaceo." But the supposed collemaceous structure appears not to 

 be made out, and the plants are perhaps therefore better taken, as by 

 Nylander (comp. Enum. Gen. p. 140, note) as expressing an aberrant 

 type of the Lecideei. 



Lecidea (Psora) Russellii, sp. nov. : thalli squamis crassis Itevi- 

 gatis subimbricatis undulato-lobatis e pallide viridi rufescentibus subtus 

 margineque albis ; apotheciis sessilibus, margine obtuso flexuoso rufo 

 discum e subconcolore viridi-nigrescentem demum tumidulum cin- 

 gente. Sporse incolores, ellipsoideae, limbatse, diam. 2 - 21-plo lon- 

 giores. On lime-rocks, Burlington, Vermont, Mr. Russell; and at 

 Brattleborough, on schist, 3fr. Frost. Northward, at Behring's Straits, 

 Mr. Wright. Frederick County, Maryland, on lime-rocks. Alabama, 

 on the same rocks, Mr. Peters. Texas, (on the earth, and in crevices 

 of lime-rocks near the Blanco,) Mr, Wright. Jurassic rocks, head of 

 Powder River, Rocky Mountains, Dr. Hayden. Scales at first closely 

 appressed, smooth, from pale-greenish becoming brownish, and at length 

 reddish-brown ; the ascending white-powdery margins waved and 

 sinuously lobed ; white beneath. Apothecia middling-sized or largish, 

 sessile ; the thick, reddish-brown, shining, at length flexuous margin 

 (which becomes sometimes paler, or white-powdery) finally excluded 

 by the convex, rufous, at length greenish-nigrescent disk. Rather 

 resembling L. testacea than L. glohifera ; but the colors appear to dis- 

 tinguish it. The lichen has also much of the aspect of fine specimens 

 oi Lecanora cervina, a, glaucocarpa. The disk is pale-brownish within, 

 and rests upon a pale hypothecium. — The genus Biatora, in the sense 

 of Fries, much as its separation facilitated the study of an obscure 

 tribe, appears hardly maintainable, otherwise than as a section of 

 Lecidea ; and that part of it to which the present and next-followino- 

 species belong {Psora, Massal.), though obviously analogous to the 

 squamulose Lecanorei (Squamaria and Placodiiim, DC, Nyl,, Placo- 

 dium, Auct.) is by no means so easily to be distinguished. The spores 

 furnish an elegant criterion of the affinity of species, but the significance 



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