Greville^ on New Diatoms. 
85 
invariably and decidedly concave. In the present species 
they are (apart from the trifling curve of the angle) per- 
fectly straight. Then^ I have never seen T, insigne with 
anything more than a row of puncta^ cutting off the angles ; 
whereas in T. definitum, an actual line is quite conspicuous. 
It may also be remarked that the angles are not rounded 
(to the extent of the segment of a circle) as T. insigne, but 
are rather ovate in outline. The distance between the angles 
is •0028''_, and the marginal puncta 8 in "OOl"". 
Triceratium unguiculatum, n. sp.^ Grev. — Large; valve 
with 4 angles^ very concave sides^ and rather large hexagonal 
cellules; angles somewhat obtuse_, furnished with a minute 
claw-like process. (Fig. 9.) 
Hab. Barbadoes deposit^ Cambridge estate; C. Johnson, 
Esq. ; R. K. G. 
Of this, one of the most distinct and constant species in 
the whole genus, I have examined a number of specimens. 
The hexagonal cellules (6 in 'OOl'") are uniform in size, and 
form a delicate reticulation. The most remarkable feature, 
however, in the valve is the slender claw-like process which 
seems to occupy the place of pseudo-nodule, and to arise from 
a small callous base just within the angles. Distance be- 
tween the angles '0040''. 
Triceratium plumosum, n. sp., Grev. — Large; valve with 
nearly straight sides and broadly rounded angles ; structure 
composed of a central large umbilicus, from which radiate 
plumose lines of hexagonal cellules ; pseudo-nodules absent. 
(Fig. 4.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
An exceedingly beautiful species, and as distinct as the 
preceding. The radiating lines of cellules are very narrow 
as they originate from the umbilicus, and gradually increase 
in size until they are about 7 in -00 T'. As they proceed 
they keep giving off new lines to fill up the space, and near 
the margin the cellules again diminish in size, especially 
within the angles. Diameter between the angles '0060'^ 
Entogonia. 
Entogonia reticulata, n. sp., Grev. — Valve with nearly 
straight sides and obtuse angles with extremely prominent 
pseudo-nodules; compartments of the border minutely but 
distinctly reticulato- cellulate ; central triangle with fine radi- 
ating costse. (Fig. 5.) 
