O’Mrara—Report on the Irish Diatomacee. 273 
(a.) Surfaces of the valves not undulate. 
Biddulphia radiata, (Wm. Sm.) Marine. 
Valve nearly circular; cellules distinct, roundish, radiate, larger 
at the margin than towards the centre, where they are small and more 
distant; processes two, large, alternating with two others smaller and 
spine-like, 
It is with some difficulty that I have come to the conclusion that 
this form is identical with that described by Wm. Smith, first as 
Eupodiscus radiatus, B.D., Vol. i., p. 24, Pl. xxx., fig. 255; and sub- 
sequently as Biddulphia radiata, Vol. u., p. 48, Pl. lxi., fig. 255. 
Neither as regards the outline of the valve, nor its areolation, can this 
form be regarded as obviously the same as that described in Smith’s 
figure, which is perfectly orbicular, whereas in the present case the 
outline, though nearly circular, presents four distinct angles, the pro- 
cesses being placed at opposite ends of one diagonal line, the spines 
occupying the corresponding position on the other. Roper, Q.J.M.S., 
Oct., 1658; p. 19, Pl. ii, fig: 29, and Ralfs, am Pritch., p. 847, 
affirm the orbicular outline of the valve; but Smith, who was sub- 
sequently convinced that the form was wrongly placed in the genus 
Eupodiscus, and that its proper position was in Biddulphia, uses such 
language as to imply that the outline is not perfectly circular. Mark- 
ing the distinctive peculiarities of Eupodiscus and Biddulphia, he 
says, the frustules of the former differ from those of the latter, ‘‘ by 
the orbicular outline of their valves.” B.D., Vol. i., p. 48. The 
present form differs from Smith’s figure not only in the outline, but 
in the character and arrangement of the cellules. In the latter, the 
cellules are minute, close, and not radiately disposed, and on this point 
Ralfs alleges, ‘‘the cellules are not radiant,’ Pritch., p. 847. The 
specific name given to the species by Smith is, however, suggestive 
of the thought that the figure is at fault in this respect. Roper’s 
figure of the species exhibits the cellules as small and radiately 
arranged, but in his description he represents them just as they are in 
the form under consideration, ‘‘as distinctly reticulated, with small 
but rather irregular hexagons.”’ 
Cerataulus Smithu, Ralfs, in Pritchard, p. 847. Cleve, Om 
Svenska och Norska Diat., p. 218. Rab. FI. Eur., sect. i., p. 318. 
Salt marsh near Ballysodare, Co. Sligo. 
Biddulphia turgida, (Ehr.) Marine. 
Connecting zone transverse; valves nearly orbicular, having two 
large truncate processes, and two alternate spines both situated diago- 
nally; a circlet of small marginal spines sometimes present, and 
numerous minute spines scattered irregularly over the surface; stria- 
tion minutely punctate, the puncta arranged in close wavy lines. 
This, as well as the former species, are by Ralfs, Heiberg, Raben- 
horst, and Cleve, placed in a distinct genus named Cerataulus, the 
