GrevillEj on Aster olamprae. 
49 
some of tlie lateral ones projecting. Diameter -0024 to 
•0040". (Figs. 26, 27). 
Craspedodiscus semiplanus, Brightw., ^ Mic. Journ./ vol. 
viii, p. 95, pi. vi, fig. 12 (imperfect). 
Hab. Barbadoes deposit; Brightwell, Balfs, T. G. Rylands, 
B. K. G. 
Bather rare, and seldom quite perfect. It is the most 
convex of all tlie Barbadoes species, and is aptly compared by 
my friend, Mr. Bylands, to a Medusa. In several respects 
it possesses peculiar characters. The umbilicus is eccentrical. 
The rays are not equidistant, as in all the other species of 
the section^ but are more widely separated on the side where 
the umbilical lines are shortest. On the opposite side, 
where the lines are longest, two or three of the segments are 
much smaller than the rest, and it is in these that the lateral 
cellules project most prominently. I find two varieties, 
which, in a larger series of specimens, would probably be 
found to run into each other — one with the cellules of the 
inner margin of the segments comparatively small and 
numerous; the other having them considerably larger, 
and fewer, and the valve furnished with a greater number of 
rays. In the first-mentioned variety the prevailing number 
of rays is seven : in the second eight or nine. Mr. Balfs 
justly remarks Pritch. Infus.,^ p. 939), that Mr. Brightweirs 
figure must have been taken from an imperfect specimen, 
being deficient in one of the umbilical lines ; and that the 
diatom is closely allied to Asterolampra. As the name be- 
stowed upon this species indicates a formation common, in a 
greater or less degree, to the majority of the Barbadoes 
Aster olamprce, I have ventured to change it, and to confer 
upon it that of its estimable discoverer". 
III. Segments, with their inner margin punctate ; lateral 
cellules large, wedge-shaped, united. 
9. Asterolampra Rylandsiana, n. sp., Grev. — Segments 
punctate, with large, wedge-shaped, united lateral cellules ; 
.narrow portion of the rays obsolete. Diameter about "0018" . 
(Figs. 28, 29). 
Hab. Barbadoes deposit; T. G. Bylands, De Brebison, 
B. K. G. 
A most peculiar species, and constant in its leading cha- 
racters. At the first glance, the valve is conspicuous for a 
circle of large geminate cellules, which, when they come to 
be close examined, prove to be the lateral cellules of the seg- 
ments in such close juxta-position as to render the narrow 
portion of the rays obsolete. There are no other large cel- 
lules belonging to the segments, the whole of the remainder 
