418 PROCEEDINGS OF THE AMERICAN ACADEMY 



and value of the sporal diflferentiation seem not yet sufficiently well 

 understood to make this a safe guide, or, at least, more than a guide, 

 in the distinction of genera ; as it surely is an insufficient ground, in 

 the case of such constructions as Synechoblastus, Trevis., and Mene- 

 gazzia, Ochrolechia, Secoliga, Massal., &c. And this opinion, which, 

 it is proper to say, has resulted from the description and preparation 

 for publication of more than ninety North American, beside numerous 

 other species referable to Lecidea, as understood by Acharius, during 

 which constant use has been made of the instructive works of Koerber, 

 as well as of the earlier writers of the same school, is in accordance 

 with, as it was first suggested by, the only universal system of Lichenes 

 of the present day, — that of the learned Dr. Nylander. This species, 

 which is perhaps the finest representative of Lecidea known to Noi'th 

 America, is dedicated to our colleague, my valued friend and fellow- 

 student of the Lichenes, the Rev. John Lewis Russell. 



Lecidea (Psora) luridella, sp. nov. : thallo squamoso imbricato 

 e viridi-cervino fuscescente, squamis parvulis appressis laevigatis sub- 

 crenatis ; apotheciis adnatis convexis immarginatis rufo-nigris. Sporai 

 octonoe, parvulce, incolores, ovoideae et oblongo-ovoideoe, protopl. in gut- 

 tulas secedente, diam. lJ-2-plo longiores. On the earth. Mountains 

 of Santa Fe, New Mexico, Mr. Fendler. On the Snake Fork of the 

 Columbia River, in the Rocky Mountains, alt. G,000 ft., Dr. Hayden. 

 Scales of the thallus much smaller, and also thinner, than those of 

 L. lurida and L. glohifera^ the nearest allied species, from roundish 

 becoming oblong, appressed, but the edges free, and at length a 

 little elevated, crenate, or even obscurely lobed, or also reduced and 

 glebulose, from pale-brownish with a greenish tinge when wet be- 

 coming tawny-brown. Apothecia small, adnate, convex and apparently 

 immarginate from the first, finally subglobose, from blackish-rufous at 

 length black. This little lichen (of which more than fifty excellent 

 specimens are before me) appears to approach nearest to L. lurida in 

 coloration, the thallus never showing the ferruginous tinge o^ L. glohifera, 

 and in the more appressed scales ; and to L. globifera in the convex, 

 subimmarginate, at length a little elevated fruit. I have sought in vain 

 for any clear trace of a margin. The spores scarcely furnish distinctive 

 characters in the present group {Psora, Massal.) : but those of the lichen 

 in hand perhaps agree rather with those of L. lurida, both in shape, 

 and in the variableness of the sporoblast (a feature taken into his 

 specific characterof the just-mentioned species by Dr. Koerber), though 



