90 
Greville^ on New Diatoms. 
the opportunity of expressing the satisfaction experienced 
by diatomists in general_, with the just and judicious arrange- 
ment of Mr. Ralfs with regard also to the genera Actimcyclus 
and Actinoptychus. ^' Professor Smith seems to have erred," 
remarks that eminent authority, by choosing as the type 
of Actimcyclus, not one of Ehrenberg's species, but a form 
placed in that genus by Professor Kiitzing, though really 
belonging to Actinoptychus and hence confusion arose 
between the followers of Smith and Ehrenberg. It was 
imperatively due to the latter, by what may be called the 
common law of science, that the error referred to should be 
corrected. With respect to Eupodiscus, however, a further 
revision of the genus will soon be desirable, as fomis very 
different in habit and structure are being provisionally asso- 
ciated under it. Descriptions in these papers I oflPer merely 
as adumbrationes of future systematists. 
Eupodiscus oculatus, n. sp., Grev. — Disc very convex, con- 
spicuously cellulate, with two large circular processes some- 
what distant from the margin ; extreme edge composed of a 
row of minute bead-like granules ; cellules 5 or 6 in '001". 
Diameter about '0052". (Fig. 3.) 
Hab. Monterey stone. George Norman, Esq. ; Fred. 
E. Kitton, Esq. j R. K. G. 
A splendid species, remarkable for the large processes, 
which resemble those of Auliscus, having a ring-like border. 
The celiulation is tolerably uniform in general effect, but is 
irregular in shape, and the walls thick, so that in particular 
lights the surface has a somewhat pitted appearance. Towards 
the margin the cellules are rather smaller, and occasionally 
present a semi-radiate character, not in any degree perceptible 
in the rest of the disc. The row of minute granules at the 
extreme edge, when clearly seen, are extremely beautiful. 
Eupodiscus obscurus, n. sp., Grev, — Disc very convex, 
with four circular marginal processes, and two or three 
minute internal marginal tubercles between them ; cellules 
very minute, 30 in -001'', in the centre of the disc. Diameter 
•0028". (Fig. 4.) 
Hab. Cape of Good Hope ; Dr. Macrae. 
The structure in this species is more dense than in any 
other hitherto described, and not clearly visible except with 
the aid of a good instrument and favourable light. I was 
myself unable to measure the celiulation with certainty, but 
my friend Mr. T. G. Rylands has determined the cellules to 
be 30 in -001" in the centre^ and 42 in -001" at the margin 
of the disc. 
