O'Meara — Report on the Irish Biatomacece. 273 



(a.) Surfaces of the valves not undulate. 



Biddulpliia radiata, ("Wm. Sm.) Marine. 



Valve nearly circnlar ; cellules distinct, roundish, radiate, larger 

 at the margin than to-^ards 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 hy "Wm. Smith, first as 

 Eupodiscus radiatus, B.D., Yol. i., p. 24, PL xxx., fig. 255 ; and sub- 

 sequently as Biddulphia radiata, Yol. ii., p. 48, PI. Ixii., fig. 255, 

 !N^either 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, thoxigh 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., 1858, p. 19, PI. ii., fig. 29, and Ralfs, in Pritch., p. 847, 

 ■afiirm 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 diifer from those of the latter, "by 

 the orbicular outline of their valves." B. D., Yol. ii., p. 48. The 

 present form diUers 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 Smithii, Ralfs, in Pritchard, p. 847. Cleve, Om 

 Svenska och liorska Diat., p. 218. Rab. El. Eui'., sect, i., p. 313. 



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 sui'f ace ; 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 



