4 
GrevillEj on New Diatoms. 
the hexagonal spaces. In the centre of the disc the cellules 
are 4 — 5 in -001'". 
Cos cino discus ohlongus, n. sp., Grev.— Disc more or less 
oblong, having the centre depressed, and an umbilicus con- 
taining a number of subremote granules ; surface filled up 
with radiating granules, which diminish in size next the 
umbilicus and towards the margin, where they resemble 
minute puncta. Length -0028'' to -0050''. (Figs. 9, 10.) 
Hah. Barbadoes deposit, chiefly in Springfield estate ; 
C. Johnson, Esq.; L. Hardman, Esq.; R. K. G. 
This beautiful little species is liable, on account of its 
similarity in form, to be taken for a variety of C. punctatus 
of Ehrenberg; but on a close examination it appears to be 
essentially difi'erent from the figures of that diatom in ^Mikro- 
geologie.' The grannies forming the radiating lines, for 
example, become smaller as they approach both the margin 
and umbilicus. The latter is not smooth, but always con- 
tains a number of granules, which, in the more elongated 
valves are generally arranged in lines. The centre of the 
valve is also much depressed. C. jmnctatus itself, however, 
is not very clearly established. Ehrenberg gives two figures 
('^Mikr.'' Tab. xvii, figs. 40, 41), the first of which is oval, 
but neither of them exhibits the slightest indication of one 
of the most conspicuous characters contained in the descrip- 
tion, viz., cellules "very densely crowded at the margin, 
and forming a broad yellowish- white border.^'' At present I 
am under a very strong impression that two or three oval or 
oblong species belong to the American deposits, one of which 
may be the diatom Ehrenberg had in view. 
Brightwellia. 
Brightwellia Johnsoni, Ralfs, MS. — Valve with the border 
composed of radiating lines of cellules diminishing in size 
from the coronal circle to the margin, and of ridge-like ribs 
at subregular intervals. Diameter about '0035.'' (Fig. 11.) 
Hab. Barbadoes deposit, Cambridge and Springfield 
estates, most abundant in the latter; C. Johnson, Esq.; 
L. Hardmann, Esq. ; R. K. G. 
This exquisitely beautiful diatom is similar in size to 
B. elaborata, bat is at once distinguished by the radiating 
lines of cellules becoming smaller towards the margin, and 
by the dark ribs which radiate, at short intervals, parallel 
with them. The coronal circle of larger cellules and the 
spiral arrangement of the central cellules are very like the 
