44 
Greville^ on Aster olampr(S. 
dubia, and aliena, tlie pore is exactly opposite the end of the 
rays ; in A. Kittoniana it is on each side of the narrow por- 
tion of the ray, about the middle. Similar pores exist in 
various discs from the Barbadoes deposit_, which seem to 
belong to the genus Liostephania. There appears_, indeed, 
to be a transition from this section of Asterolampra to that 
genus j and it will probably be found that the genera just 
named, along with Rylandsia, and possibly Actinogonium, 
may be conveniently united into a family. Of Dictyolampra 
of Ehrenberg, which has been associated with Actinogonium 
and Liostephania, Mr. Ralfs justly remarks, that it ''^differs 
from the other genera of this family (the Melosirece) by its 
disc being cellulate only in the centre ; and, indeed, it prob- 
ably ought, together with Liostephania and Actinogonium, to 
form a distinct family ; but, having seen no specimens, we 
are unable to decide on their proper position.^^ (Prit. Inf., 
1861, p. 813.) I labour under the same disadvantage as my 
friend Mr. Ralfs, and have only to suggest whether Dicty- 
olampra may not be more closely allied to my genus Stictodis- 
cus. Indeed, it very nearly resembles S. Calif ornicus . 
There is something so peculiar in the general aspect of the 
diatoms of the second section, that at first sight materials 
would appear to exist for the construction of a genus which 
would relieve Asterolampra from its most aberrant forms. 
But unfortunately frustules occur which partake of the cha- 
racters of both sections. A. IcEvis is a transition species. It 
is the only one in the first section in w^hich the segments are 
smooth ; but it has at the same time slender umbilical lines, 
and wants the central nucleus. On the other hand, A. simu- 
lans possesses the nucleus and thick umbilical lines of the 
second section, while the segments show the large oblong 
cellules, and minute marginal punctation characteristic of 
various species of the first. 
Section I. — Umbilicus simple or cellulate (not with a 
thickened nucleus) . Umbilical lines slender. 
I. Segments of valve having their inner margin composed 
of punctiform cellules. 
1. Asterolampra Marylandica, Ehr. — Diameter '0015'' to 
•0021". (PI. VII, figs. 1—3.) 
Hab. Barbadoes deposit, very rare ; with four rays, T. G. 
Bylands, R. K. G. ; with five rays, T. G. Bylands ; with six 
rays, R. K. G. 
All the specimens I have seen of the discs which I refer 
to this place, are diminutive in size, and deviate somewhat 
from the ordinary condition of the species. A. Marylandica, 
