BRIGHTWELL, ON RHIZOSOLENIA. 93 
the section in which Kutzing has placed it (from using an 
inferior microscope), as the striz are very conspicuous with a 
good lens, being as few as 33 or 34 in ‘001. It differs from 
the true A. brevipes of Agardh, by the elliptic-oblong obtuse 
valves ; from A. subsessilis by the usually numerous frustules 
and the distinct and somewhat elongated stipes; and from 
both by the much finer striz. 
Remarks on the Genus “ RuizosoLventa” of EHRENBERG. 
By Tuomas Bricutwe.t, Esq., F.L.S., Norwich. 
Amone the remarkable forms lately detected in Ascidie 
and Noctiluce, specimens have been found of some which 
appear to belong to the genus Rhizosolenia, of Ehrenberg. 
Having had, in this case, as in that of Chetoceros, an op- 
portunity of examining the species in a tolerably perfect 
state, we hope to be able to exhibit the true character of 
several more of those fragmentary and unsatisfactory forms 
which Ehrenberg, mm his various works, and particularly his 
‘ Microgeologie,’ has, as we conceive, too hastily and inju- 
riously to science, erected into genera and species. 
The characters given by him of the genus Rhizosolenia 
are “lorica tubular, with one extremity rounded and closed, 
while the other is attenuate and multifid, as if termimatimg 
in little roots.” He describes five species, some of which 
do not at all agree with the above characters; and the late 
Professor Bailey added a sixth under the name of R. hebe- 
tata. The greater part of these supposed species are, as we 
believe, only fragments of the silicious organisms we are 
about to describe, or of kindred species, and to enable the 
reader to judge of the correctness of our views, we have 
given copies of several of Ehrenberg’s published figures, as 
well as figures of all our newly-discovered perfect forms. 
Ehrenberg’s five species are* 
1. Rh. Americana, from Virginian earth. Of this he 
gives no less than eleven figures, most of them certainly not 
belonging to this genus. 
* These species (and a sixth clearly not belonging to it) are described in 
Kutzing’s ‘Species Algarum,’ p. 24, where the references to Ehrenberg’s 
works or papers, in which they first appeared, are to be found. 
