24 
Descriptions of New and Kare Diatoms, Series XV. 
By R. K. Greville, LL.D., F.U.S.E., &c. 
(Plates III & IV.) 
(Communicated by T. C. S. Ropee, E.L.S., &c Read 8th March, 1865.) 
Clavularia, n. gen., Grev. 
Erustules free, linear- elongated, with numerous transverse 
pseudo-dissepiments interrupted by a central, smooth, ex- 
ternal plate. Valve linear, with a central inflation, and a 
longitudinal row of strong puncta on one of its margins, 
which, in the front view, are shown to he the heads of short 
suhcapitate processes. 
It is very difficult to define this exceedingly curious 
diatom; indeed, it would be hopeless to attempt to do so 
without the aid of figures. For two years I was only ac- 
quainted v» ith the valve ; and when I subsequently met with 
several specimens of the entire frustule, I should scarcely 
have ventured to identify them as belonging to the same 
thing, if I had not fortunately discovered an individual in an 
oblique position, which left no doubt whatever of the fact. 
I shall leave it to other diatomists to speculate on the 
affinities of this strange-looking production. 
Clavularia Barbadensis, n. sp., Grev. — (Figs. 1 — 3, PI. III.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
Frustule -0060" to -0080" in length, and scarcely -0002^' 
in breadth, perfectly linear, except at the acute apices, 
having narrow margins, one of them (which I call the upper) 
strong and coloured. Numerous transverse dissepiments 
occur throughout the whole length, at irregular intervals, 
except for a space of about *0014" in the middle, which is 
occupied by a smooth lamina, folded up, as it were, and 
pressed against the surface, and so concealing the dissepi- 
ments, convex above, where it is on a level with the coloured 
margin, and gradually tailing off below into the uncoloured 
margin. Along the upper margin are situated a row of very 
short, stout, subcapitate processes, standing up like little 
nails, at irregular distances, evidently arising out of the sub- 
stance of the margin itself, and of the same colour, and 
having no reference to the pseudo-dissepiments. The num- 
ber of these processes varies; two generally, but sometimes 
three or four, belong to the centre, and between the centre 
