E-OPER^ on Biddulphia. 
19 
I believe it is the first time that any signs of the reproductive 
process have been noticed^ in any species of the genus. 
I have a few orbicular valves from the Thames^ vrhich 
appear to belong to the present species^ but I have not met 
with a perfect frustule in any English gathering. 
13. Biddulphia radiata, Smith (sp.) 
Valve orbicular_, distinctly reticulated^ with small, but 
rather irregular hexagons ; processes short, broad at the 
base, reticulated and rather obtuse, with two short sub- 
marginal spines midway between them ; connecting mem- 
brane faintly striated. (Plate II, figs. 27, 28. 29,) 
Marine or brackish water. Thames and Orwell, Mr. T. 
West ; Barking Creek, Eoper ; Gorleston, Col. Baddeley. 
S^n. EupoDiscus EADiATUS. Smith, Sjn., 1853, vol. i, t. xxx, f. 255 ; 
vol. ii, t Ixii, f. 255. 
The late Professor Bailey described, in his ' Microscopical 
Observations in South Carolina,' &c., published by the Smith- 
sonian Institution in 1850, a species of Diatom under the 
name of Eupo discus radiatus, with the following brief cha- 
racters : " In form, size, and reticulation resembling the 
Coscinodiscus radiatus of Ehrenberg, but having four (or 
more) foot-like projections near the margin.'^ But there is 
no figure given, and though he states it is a common form 
in the South of the Union, I have been unable to meet with 
specimens. Professor Smith has adopted this name for the 
species now under discussion ; but, in his specific character, 
states that the ' cells ' are circular, whereas, in Coscinodiscus 
radiatus, to which Bailey compares his form, they are dis- 
tinctly hexagonal ; whether the two forms are synonymous I 
am unable to say with certainty, but, as I stated in a pre- 
ceding number of the Journal,"^ I feel convinced that the 
generic position assigned to it in the ' Synopsis' cannot be 
maintained, as the wiiole structure of the valve and pro- 
cesses diff'ers materially from any of the genuine Eupodisci. 
In that genus the projections are apparently hyaline sili- 
ceous tubes, rising immediately from the surface of the valve, 
without any trace of structure whatever, and I am not aware 
that any species has long spines ; the connecting membrane 
also is simply a circular ring, as in Coscinodiscus. In the 
present species, however, there are two processes, agreeing 
exactly in structure with those in Biddulphia, reticulated in 
the same manner as the valve itself, nearly to their points, 
and between them two acute spines; and the connecting 
* 'Mic. Jour./ vol. vi, p. 19. 
