RoPER^ on the genus Licmophora. 
53 
At fig. 22 I have given a figure of a specimen observed by- 
Mr. G. Norman in shell cleanings from Japan. I do not 
venture, on the strength of a single specimen, to describe it 
as a distinct species. It comes nearest to A. ccelatus, but 
differs in the sharp and diffused character of the punctation, 
and especially in the presence of puiicta on the converging 
lines. 
On the genus JjiCMOvno^K (Agardh). 
By F. C. S. Roper, F.L.S., &c. 
(Read March 11th, 1863.) 
The microscopic forms of Algse of the order Diatomacess^ 
although slightly alluded to in the works of Dillwyn in 1809, 
and, with respect to a few genera, more carefully investigated 
by Dr. Greville, in the ^ Scptt. Crypt. Flora ' and ' British 
Flora,^ and since then in the papers of Messrs. Ralfs and 
Thwaites in the ' Ann. Nat. Hist.,^ had not been made the 
subject of any special work in this country, until the liberal 
guarantee offered by Messrs. Smith and Beck induced the 
late Professor Smith to publish the result of his labours in 
that hitherto neglected branch of science; as although in 
the earlier editions of Pritchard^s ' Infusoria,^ a portion of 
Ehrenberg's descriptions of the Diatomacese, with copies of 
his figures, were given, these were so imperfect and meagre, 
and included so many foreign forms, that they were of little 
use to elucidate our British species. 
Our native microscopists, although universally admitted to 
have the best instruments, and therefore the best means of 
investigation in their hands, had treated the siliceous epi- 
derms of the Diatomacese more as objects for testing the 
powers of their respective instruments than with any endea- 
vour to arrive at a satisfactory conclusion as to their relative 
habits, modes of growth, or position in the scale of nature. 
The labour of reducing to anything like a system the varied 
and often widely discordant opinions on these minute forms 
of the vegetable kingdom was thus left almost entirely in 
the hands of continental observers, and the works of Agardh, 
Kiitzing, Ehrenberg, Nitzsch, De Brebisson, and others, show 
the patience with which — with the imperfect instruments at 
their command — they reduced the chaos previously existing 
to something like order. But the difficulty of giving accurate, 
or, at least, generally recognisable descriptions of such minute 
forms is so great, that though the voluminous works of Kiitzing 
and Ehrenberg are invaluable in determining those species 
