20 ROPER, ON BRITISH MARINE DIATOMACE. 
From a careful examination of the figures in Ehrenberg’s 
‘ Microgeologie,’ I consider this species may be synonymous 
with his Coscinodiscus limbatus, t. xx, f. 29, or Cos. fimbriatus, 
t. xxii, f. 2, but there is no pseudo- nodule given in the figures, 
and without authentic specimens it is impossible to refer it 
with any certainty to either of these species. 
Coscinodiscus concinnus.—‘ Synopsis,’ vol. 1, p. 85. 
Marine. Caldy, Pembrokeshire, Rev. J. Guillemard ; 
Humber, Mr. Norman (fig. 12). 
This interesting species, discovered by Professor Smith, 
and described in the Appendix to vol. 11 of the ‘ Synopsis,’ 
occurs with tolerable frequency in the Caldy gathermg, and 
I have received remarkably fine specimens, through the 
kindness of Mr. Norman, from dredgimgs in the Humber. 
Although not a new form, it has not yet been figured, and as 
the large size of the specimens enables me to add some further 
points to those already given by Professor Smith of the 
peculiarities of its structure, I may be excused for cluding 
it in these notes. 
The description given in the ‘Synopsis’ is as follows: 
“ Cellules arranged im radiating lines, equal except im centre 
of valve, where there occur three to eight larger cellules ; 
cellules 24 im 001"; diameter :0025" to -0056."” This is 
perfectly correct as far as it goes, except as to size, my 
specimens ranging from ‘004 to -013”, or nearly double 
the size of Professor Smith’s. But the larger specimens 
show plainly a point that is not easily discernible in those 
under ‘O04 in diameter, namely, a submargmal row of 
minute spines varying from ya4yoth to zo!)pth of an inch apart, 
according to the size of the disc, and from each of which 
there is a radiating line almost to the centre of the valve. 
The celiules themselves are hexagonal and formed on the 
same peculiar plan as already described im Eupodiscus 
tesselatus, and shown im fig. 1 8 The large irregularly 
formed cells in the centre havi ing hkewise dots at their a angles. 
The valve is very convex ; so much so in the larger specimens, 
that when the central cells are in focus with a high power, 
the circumference is almost invisible. It differs in this 
respect from Cose. per, foratus, to which it is most nearly 
allied, that species having much the form of a lmette watch- 
elass, flat im the centre, with a narrow sloping margin. The 
cellules are also much smaller in C. concinnus. 
With these new facts the following description might be 
given of the species: “Valves very convex, with minute 
hex xagonal cellules arranged in radiating lines, divided at 
