50 
Greville_, on Aster olamprce. 
of tlie space being minutely punctate. The number of rays 
varies from seven to twelve. The umbilicus is sometimes 
simple ; but the majority of specimens contain a few centrical 
cellules. The whole valve has a striking resemblance to the 
disc of an Ophiocoma deprived of its rays ; the geminate cel- 
lules representing the parallel plates or scales which are seen 
opposite the origin of each ray in that genus of Radiata. 
IV. Nearly the whole surface of the valve filled up with 
radiating puncta. Segments forming an undulating marginal 
annulus. 
10. Asterolampra marginata (Bright)^ Grev. — Two thirds 
of the radius of the valve occupied with radiating puncta ; 
umbilical lines very short; segments forming a narrow^ 
punctate border ; narrow portion of the rays obsolete. Dia- 
meter about '0038". (Fig. 30). 
Craspedodiscus marginatus, Brightw.^ ' Mic: Journ.^ vol. 
viii^ p. 95, pi. V, fig.. 7. 
Hab. Barbadoes deposit j Brightwell^ T.G.Rylands, E/.K.|G. 
In this exceedingly beautiful diatom we find a remarkable 
deviation from the ordinary relative proportions of the several 
parts. The greater portion of the disc is filled up with 
puncta_, which are not irregularly arranged like the umbilical 
cellules in former species, but radiate from the centre. The 
hyaline area is reduced to a narrow ring, and the segments 
to a mere waved border ; the narrow portion of the rays 
having consequently no space for development. The rays 
are numerous, generally from fourteen to twenty. There 
can be no question that Mr. Ealfs was correct, when, with 
his usual acuteness, he referred this interesting diatom to 
the Aster olamprce. 
V. Segments represented by a deltoid ramification of the 
umbilical lines. 
11. Asterolampra Ralfsiana, n. sp., Grev. — Umbilical lines 
as they approach the margin dividing dichotomously into 
equal deltoid sections; centre very irregularly cellulate. 
Diameter about -0033". (Fig. 31). 
Hab. Barbadoes deposit ; Ralfs., T. G. Eylands, B. K. G. 
This is, without exception, the most extraordinary species 
in the genus. The umbilicus is invariably cellulate, and 
the cellules very irregular and unequal in size. One of them 
is considerably larger than the rest. About half way between 
these cellules and the margin of the valve, the umbilical lines 
begin to divide in a dichotomous manner, until, by the time 
they have reached the margin, they have described a series of 
conical or deltoid figures, all of equal diameter. These deltoid 
