328 On a new genus of Diatomacea?. 



XLI. — On a new Genus of Diatomacese. By the Rev. M. J. 

 Berkeley and J. Ralfs, Esq. 



[With a Plate.] 



The Aberdeenshire coast, though far from rich in the higher 

 order of Algse, has rewarded the researches of Dr. Dickie with 

 one or two species of great interest. In those which are more 

 or less intimately related to Schizonema, on the contrary, several 

 species have occurred no less remarkable for their large size 

 and unusual form than for their beauty. One of these is so 

 anomalous, having a central thread containing frustules, as in 

 Schizonema, surrounded by a highly developed cellular coat, and 

 at the tips extending beyond it, that it has been thought desi- 

 rable to "wait for maturer observation, should another season 

 prove favourable, by a renewed examination of the structure, 

 rather than to publish it as a pendant to the present short notice. 

 The species which we have now the pleasure of dedicating to 

 its discoverer, Dr. Dickie, is remarkable for its flat ulva-like frond 

 and its pale purplish tint, and cannot be associated with any 

 known genus. Its habit at once removes it from Schizonema, 

 whether taken in a more confined sense and limited to the spe- 

 cies with a compound frond, or comprising Micromega and such 

 species as S. Dillwynii : from Encyonema, of which Monema 

 prostratum is a synonym, by its straight, not cymbiform frustules : 

 from Homceocladia by its short, not elongated frustules, as also 

 by its habit ; and from Berkeley a again by habit, and by the want 

 of a gelatinous base. Whether Kiitzing has anything more nearly 

 allied to it will be seen on the publication of his great work on 

 Diatomacea, especially as we have communicated this curious 

 production to him under the name which we are now about to 

 record. 



Dickieia, Berk. andRalfs. 



Frons subgelatinosa, tenera plana deorsum attenuata, undulata, 

 apice obtuso. Frustula oblonga sparsa simplicia vel binata an- 

 gulis puncto orbiculari notatis. Alga marina vernalis pallide pur- 

 pureo-alba. Nomen dedimus in honorem Doct. G. Dickie Al- 

 garum peritissimi scrutatoris. 



Dickieia ulvoides, Berk, and Ralfs. 



Hab. In shallow pools between high and low water mark with 

 Schizonema comoides and other allied forms. April 20, 1844. 

 Aberdeen, Dr. Dickie. 



Frond 1 — 1 \ inch high, resembling young specimens of Por- 

 phyra vulgaris, but of a very pale purplish white hue, a gelatinous 

 consistence, and entirely free from any cellular tissue ; lanceolate, 

 much attenuated below, rather obtuse above, and sometimes, 



