Collins and Howe: Species of Halymenia 177 



as are shown by a microscopic comparison of the vegetative 

 characters of these two superficially similar plants. The cysto- 

 carp of H.floridana, however, is commonly somewhat protuberant 

 on both faces of the frond, while that of H. Gelinaria is commonly 

 protuberant on only one face. In both, the spore-mass or "nu- 

 cleus" is very dense, turbinate or oblate-spheroid, sometimes 

 apparently two- or three-lobed, and is supported by a short stalk. 



In 1900 (Phyc. Bor-Am. 750) the senior author of the present 

 paper used the name " Halymenia floridana forma dentata (Crouan) 

 Collins" for a dentate-margined condition of the present species, 

 citing Gelinaria dentata Crouan in Maze & Schramm, Algues de 

 Guadeloupe, as a synonym. In doing this he was, in effect, 

 adopting the opinion (expressed in litt.) of a distinguished phy- 

 cologist who was familiar with the Guadeloupe specimens dis- 

 tributed by Maz6 & Schramm but knew Halymenia floridana 

 J. Ag. from description only. However, the Maze, Alg. Guad. 

 no. 1602, "Capesterre, Plage du bourg" in the herbarium of 

 the British Museum, is certainly very different, as to species, at 

 least, from either H. floridana or H. Gelinaria. Whatever may 

 be the relation of other Guadeloupe specimens to these two 

 species, the name dentata of Crouan, a "nomen seminudum" at 

 best, can not, under the provisions of the "American Code" at 

 least, be adopted for either, on account of the previously published 

 Halymenia dentata Suhr. 



Halymenia Gelinaria adheres very firmly to paper when dried 

 under pressure. 



Halymenia pseudofloresia sp. nov. 



Thallo violaceo-rubro, brevi-stipitata; stipite inferne subtereti, 

 superne cuneato; fronde juvenili membranacea, gelatinosa, aetate 

 provecta firmiore et subcoriacea, 50-450 p, crassa, circumscriptione 

 suborbiculari, ovata, cuneato-obovata, vel nonnunquam valde 

 irregulari, longitudine 7-30 cm., profunde lobata vel prolifica- 

 tionibus stipitatis munita; rachidibus 1-8 cm. latis, lobis et pro- 

 lificationibus plerumque lanceolatis, serratis vel seriebus loborum 

 etc. secundariorum munitis; superficie haud nitente, plerumque 

 plana, sed aetate provecta minute verruculosa; medulla frondis 

 laxa, subvacua, filamentis sparsis percursa, filamentis trans- 

 versalibus crebris, filamentis stellatis paucis, inconspicuis; strato 

 subcorticali indistincte filamentoso, cellulis 20-50 ix diam. ; strato 



