98 
Greville, on New Diatoms. 
with minute radiating puncta^ and 8 rib-like lines ; centre a 
smooth nodule^ giving off 2 simple,, diverging, cylindrical, 
flatly capitate processes. Diameter '0020'^ (Fig. 3.) 
Hab. Barbadoes deposit, Cambridge estate; in slides com- 
municated by C. Johnson, Esq. ; very rare. 
I venture to place this little diatom in the genus Thauma- 
ionema because the only material difference seems to lie in 
the absence of the little stalk which supports the diverging 
processes. They seem, in the present instance, to spring at 
once from a smooth, prominent, central nodule, but the 
flat dilated apices are so similar to those in the genus above 
mentioned that they may be regarded with some confidence 
as articulating surfaces. Specifically, the radiating ribs con- 
stitute an excellent character. 
DiCLADIA. 
Dicladia ? robusta, n. sp., Grev. — Large ; valves ovate- 
conical, beset with scattered minute spines, both terminating 
in a single strong horn. Diameter '0020'". Length, in- 
cluding the horns, -0055''. (Fig. 11.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. ; extremely rare. 
Both valves are furnished with strong horns, as in the 
diatom I have called Dicladia Barbadensis ; but in the present 
instance they are undivided. One of the valves is somewhat 
larger than the other, and both are sparingly and irregularly 
covered with minute spines, . a few of which are found even 
on the horns. 
Stictodiscus. 
Stictodiscus Hardmanianus, n. sp., Grev. — Large ; radiat- 
ing compartments very numerous, reaching nearly to the 
centre, with 5 — 6 transverse rows of minute puncta at the 
base, followed by a single row of pseudo-pores ; centre occu- 
pied by two circles of granules, and a minute cluster at the 
umbilicus. Diameter -0050''. (Fig. 4.) 
Hab. Monterey deposit; L. Hardman, Esq. 
An exquisite species, well distinguished by the centrical 
circles of granules and the marginal rows of exceedingly 
minute puncta. The very numerous septa arc transversely 
divided, so as to appear clathrate or ladder-like, while by 
slightly altering the focus a single pseudo-pore is observed 
in the middle of each division. 
