The Presidenfs Address. 
71 
volume of our ^ Transactions/ On the Northumbrian coast Dr. 
Donkin collected not less than 100 species_, including upwards 
of thirty which he regards as entirely new and hitherto 
undescribed^ of which he gives a detailed account_, with 
drawings of the principal species. I would say a few words 
relative to the two forms for which he proposes a new genus^ 
Toxonidea/^ Although they resemble in many respects the 
genus Pleurosigma, it is not merely in outline that they differ, 
nor that the median line loses its sigmoid character, though 
this latter is by no means an insignificant variation, but they 
appear to me to possess a true structural difference ; under a 
low power having very much the aspect of a Stauroneis. 
Under these circumstances I consider that the author has 
done wisely in thus constituting a new genus. 
With regard to another species I have a word or two to 
say, viz., Pleurosigma lanceolatum. This I think is iden- 
tical with one described and figured by Mr. Roper, in the 
October number (1857) of the ' Microscopical Journal (the 
plate being in the January number, 1858), vol. vi, pi. Ill, fig. 
11, under the designation of Pleurosigma transversale, variety 
fi'y but that gentleman conjectures that it may be probably a 
new species, a fact of which I have no doubt. Under these 
circumstances Mr. Roper would have the privilege of naming 
it. This, by the way, gives me occasion to remark, that it 
is by no means clear that the Microscopical Society has 
not been (may I say) somewhat shabbily treated with regard 
to this same paper of Mr. Roper^s ; and I am convinced that 
the author would have been better appreciated had it been 
read at the meeting of the Society ; for even if the plate had 
not appeared in the same number as the text, as is the case at 
present, the two would certainly have first come before 
microscopists together, and in all probability would have been 
published at the same time. A paper always suffers more or 
less by disunion from its illustrations, if any exist ; but with 
regard to those on the Diatomaceae this observation applies 
with increased force. 
While on this subject, having alluded to Mr. Roper^s paper, 
it may not be out of place to make one or two more remarks 
in connection with it. 
Alluding to Coscinodiscus labyrinthus , n. sp., with cellules 
hexagonal, minute, arranged in quincunx, in large irregular 
hexagonal spaces, divided by lines of confluent cellules or 
dots, &c., he says, " The arrangement of the cellules is so 
different from any yet figured, that it may be fairly entitled 
to rank as a new species.^^ Illustrations are added in the 
plate last quoted, figs. 2 a and 2 b. In the novelty of the 
