46 
GrevillEj on Aster olamprce. 
umbilical lines being invariably simple, and in the presence 
generally (though,, not always J of a nucleus of umbilical 
cellules. The number of rays in the specimens examined, 
vary from eleven to seventeen. I have only seen one in- 
dividual in which umbilical cellules were entirely absent. 
The valve, fig. 9, is the largest disc belonging to the genus 
which has occurred in the deposit. 
II. Segments having their inner margin composed of large 
elongated cellules. 
Lateral cellules of the segments not projecting beyond 
the rest. 
4. Asterolampra concinna, n. sp., Grev. — Segments pro- 
minently arched inwardly, more or less flattened at the top, 
their inner margin composed of numerous oblong cellules 
which are continued partlv down the sides. Diameter •0032'^ 
to -0040". (Figs. 10—12.) 
Hab. Barbadoes deposit ; rare ; T. G. Rylands, De Brebis- 
son, R. K. G. 
Of this beautiful diatom, I have only seen four specimens, 
all with seven rays, and destitute of umbilical cellules. The 
segments project considerably into the interior, with an out- 
line between conical and arched, and more or less flattened at 
the top. The oblong cellules which line the inner margin, 
are continued down the sides, rounding ofi* the angles. Per- 
plexing diflerences occur continually in the valves of several 
of the Barbadoes species. In the present instance, for 
example, the areolation of the segments is very much larger 
in fig. 10 than in the other two, which possibly may be 
owing to its larger size. In fig. 11, the narrow portion of 
the rays becomes somewhat ovate next the margin of the 
valve, and instead of the oblong cellules of the inner margin 
of the segments passing down the sides, there is a single 
large cellule occupying each corner, a little below the level of 
the rest. It remains to be seen whether these variations are 
of any importance. 
5. Asterolampra decor ata, n. sp., Grev. — Segments some- 
what conical, truncate, with the inner margin composed of 
very large oblong cellules, the lateral ones single, elongated, 
elliptical, reaching to the extremity of the ray. Diameter, 
•0034". (Fig. 13.) 
Hab. Barbadoes deposit ; very rare. 
Only one valve of this exquisitely beautiful disc has been 
found ; but it is so unlike any of its congeners, there can be 
no hesitation in admitting it as a species. The general 
appearance is that of a medallion containing a sort of star, 
the salient angles of which are composed of the narrow por- 
