GREVILLE, ON NEW DIATOMS. 231 
point ; median ray narrow, the rest (6) lmear, slightly dilated, 
and as if notched at the margin. Diameter 0030.” (Fig. 8.) 
Hab. Deposit at Moron, in the province of Seville; G. 
Norman, Esq., R. K. G. 
A very distinct species belonging to the section composed 
of Ehrenberg’s genus Asteromphalus, characterised by one of 
the rays being much narrower than the rest, and by two of 
the radiating umbilical rays being approximated. It appears 
to have most affinity with A. Darwinii in the angular bend 
of the median lines, but in no other feature. In a general 
sense, the valve may be called circular; but it is not strictly 
so, for in the numerous specimens I have examined it is 
more or less unequal at the margin; so much so occasionally, 
as to have a somewhat cornered appearance. The umbilical 
lines are sometimes divided near their origin, as in A. Brebis- 
soniana and A. variabilis. The rays are exceedingly well 
marked, by being invariably dilated at their marginal ex- 
tremity, and by having the appearance of being notched, or 
as if a shadow indicated a funnel-shaped termination of the 
ray-tube. ; 
TRICERATIUM. 
Triceratium Robertsianum, n. sp., Grev.—Valve with con- 
vex sides, obtuse angles, pseudo-nodules, and a wide hexa- 
gonal cellulation, the external row of cellules twice the size of 
the rest; those at the angles rounded and much smaller. 
Distance between the angles about ‘0054. (Fig. 9.) 
Hab. Curteis Straits, Queensland ; very rare ; in a dredging 
communicated by Dr. Roberts, of Sydney. 
This fine species belongs to the group of which 7. Favus is 
the type, and which requires to be carefully studied, as the 
extent of variation in 7. Favus itself is by no means clearly 
ascertained. In the rare diatom now before me there is no 
ambiguity, the outer row of large cellules being of a very re- 
markable character. The angles also are peculiar, the cellules 
which occupy them being rounded and much smaller, a 
vacant space being left immediately below the pseudo-nodule. 
The cellules in the centre are about 5 in -001”. Those of 
the marginal row scarcely 3 in ‘OU1”. 
Triceratium prominens, n. sp., Grev.—Valve with straight 
sides, obtuse angles, and very prominent pseudo-nodules ; 
centre slightly inflated; granules remote, large, in radiating 
lines, and increasing in size from the centre to the margin, 
where the lines are 4—5 in ‘001’. Distance between the 
angles ‘0040". (Fig. 10.) 
