234 GREVILLE, ON NEW DIATOMS. 
sides, obtuse angles and small circular pseudo-nodules ; 
whole area filled up with hexagonal cellules, about 5 in :001” 
in the centre, becoming smaller towards the margin. Distance 
between the angles ‘0040”. (Fig. 17.) 
Hab. Barbadoes deposit, from Cambridge estate; C. 
Johnson, Esq., J. Ralfs, Esq., R. K. G. 
A neat, well-defined species. The rather small pseudo- 
nodules filling up the slightly rounded angles are not promi- 
nent, but somewhat resemble the processes of an Auliscus. 
The cellulation becomes gradually smaller in approaching 
the margin, which is narrow, well-defined, and striated. 
Triceratium tumidum, n. sp., Grev.—Valve with concave 
sides, very rounded angles, filled with large, oval, tumid, 
minutely punctate pseudo-nodules ; surface with very remote, 
large, scattered puncta. Distance between the angles -0042”. 
(Fig. 18.) 
Hab. Barbadoes deposit, from Cambridge estate; C. 
Johnson, Esq. 
Very distinct. The pseudo-nodules symmetrically rounded 
and prominent. 
Triceratium Normanianum, un. sp., Grev.—Valve with the 
sides constricto-concave, angles dilated, widely hemispherical, 
with a transverse line at about one third of the distance 
between the lateral concavity and the summit; whole surface 
filled with minute puncta, those of the centre radiating. 
Distance between the angles about 0030”. (Fig. 19.) 
Hab. Barbadoes deposit, from Cambridge estate; G. Nor- 
man, Esq. 
Unquestionably very near 7. castellatum of West, but 
differmg from it in the lateral concavities being far deeper 
and sharper, in the lobes or angles being more widely 
dilated, in the central puncta being radiate, and in the 
transverse lines which separate the angles from the centre 
being situated nearer the ends. It appears to be an 
extremely rare species, as it has only been seen by Mr. 
Norman. 
Triceratium subcapitatum, n. sp., Grev. — Small; valve 
with straight or slightly convex sides, and. very produced, 
slender, somewhat capitate angles, having a transverse line 
near the apex; surface minutely punctate, the puncta radiat- 
ing, with 2—3 irregularly situated spines. Distance between 
the angles about ‘0020”. (Fig. 20.) 
Hab. Barbadoes deposit, from Cambridge estate; not un- 
frequent. 
The nearest ally of this minute species is 7. capitatum of 
Ralfs. That diatom, however, is almost hyaline, the central 
