ROPER, ON BRITISH MARINE DIATOMACE. 25 
present I have only met with it in one marine gathering, in 
which, however, it is not uncommon. The valve is oval, with 
the nodule dilated into a stauros, and differs from C. scu- 
tellum, var. (3, in the fineness of the dotted striz, and peculiar 
ocelli or semi-oval markings cutting off a portion, on each 
side of the valve. Professor Smith informs me that in his 
opinion they belong to the connecting membrane, but they 
appear to be rather. a thickening on the inner surface of the 
cell-wall. This species of Cocconeis is 80 very variable in size 
and appearance, that without having specimens with the 
same peculiar structure from several localities, I think it 
better to consider it as a variety, though more extended 
observation may prove that it should be classed as a distinct 
species. 
Navicula liber, var. 3.—Valve oblong, contracted towards 
the rounded extremities ; striz faint, parallel, not reaching the 
central line. Length -0033" ; breadth -OOL” (fig. 10). 
Marine. Caldy, Pembrokeshire, Rev. J. Guillemard. 
Professor Smith having, in vol. ii of the ‘ Synopsis,’ 
Liha Ehrenberg’s Nav. amphigomphus as a cuneate variety of 
N. firma. 1 refer this species with little hesitation as a 
somewhat similar variation to the nearly allied marine form 
N. liber, from which it appears to differ only m having 
bluntly cuneate extremities, and rather larger space between 
the termination of the strize and the median line. . It is pro- 
bably synonymous with Ehrenberg’s N. dilatata of the 
‘Microgeologie,’ t. u, f. 10. 
Pleurosigma transversale, var. 3.—V alve elliptical, lanceolate, 
with acute extremities, and very slightly curved median line ; 
strice aoa Length -0032" to ‘004 ; breadth -0009” to -001” 
(ig. 11). 
Marme. Caldy, Pembrokeshire, and dredged off Tenby, 
Rev. J. Guillemard. 
The typical species of P. transversale is by no means 
uncommon in both the gatherings above alluded to, whilst 
the variety here figured is rather rare. The general outline 
and structure of the valve is, however, so similar to that 
species, that having only at present met with it in these 
gatherings from Tenby Bay, I figure it merely as a variety, 
though more extended observation may prove it to be a 
distinct species. The vaives are much broader in proportion 
to the length than in the typical species, the extremities are 
acute instead of obtuse, and the median line nearly straight 
instead of having a considerable curvature. The striation 
also is finer and more difficult to resolve, than in that species. 
