Greville^ on New Diatoms, 
93 
Barbadoes deposit^ and under all its variations easily recog- 
nised hj its size,, pale colonrj and radiating^ and somewhat 
plumose^ subquadrate cellules, which are also sometimes 
more or less concentric. It is rarely that a truly symmetrical 
valve can be seen. Generally the sides of the valve differ, 
more or less, as well as the angles, even in the same specimen. 
There is no pseudo-nodule whatever, but often a slight con- 
cavity and a less conspicuous cellulation within the angles. 
Triceratium foveatum, n. sp., Grev. — Small; valve with 
straight sides and rounded angles ; surface with 6 radiating 
segments alternately raised and depressed j those terminating 
at the sides oblong, with small remote equal cellules ; the 
intermediate ones passing to the angles with cellules, larger, 
remote, unequal, and pit-like. Distance between the angles 
•0030". (Fig. 15.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides 
communicated by C. Johnson, Esq. 
This most remarkable species is so unlike any one pre- 
viously described, that it scarcely requires any supplementary 
notice. The cellules in the six compartments are not arranged 
in any regular order. Immediately within the angles is a 
cluster of very minute puncta, but no obvious pseudo-nodule. 
Triceratium firmum, n. sp., Grev. — Minute; valve with 
straight sides, rounded angles, and strong, coarsely striated 
margins ; surface filled with rather large, subquadrate, some- 
what radiating cellules ; angles minutely punctate. Distance 
between the angles -0022". (Fig. 8.) 
Hab. Barbadoes deposit, Cambridge estate; in slides 
communicated by C. Johnson, Esq. 
A stout, pretty little species; the cellules largest in the 
centre, where they are 5 or 6 in '001", somewhat radiat- 
ing, and sometimes more or less concentric. Margin thick, 
strongly defined, broadest in the middle. 
Triceratium modestum, n. sp., Grev. — Small; valve with 
strictly straight sides and rounded angles ; surface reticulato- 
cellulate, the cellules angular (not hexagonal), becoming 
smaller towards the angles, which are somewhat concave 
within and destitute of pseudo-nodules; margin striated. 
Distance between the angles '0025"'. (Fig. 14.) 
Hab. Barbadoes deposit, Cambridge estate; C. Johnson, 
Esq. 
Conspicuously reticulato-cellulate ; the cellules 5 or 6 in 
•001'', with slender walls, becoming smaller within the 
angles, but not passing into puncta. Margin at the angles 
somewhat thickened. 
Triceratium acutangulum, n. sp., Grev, — Large; valve with 
