124 
Greville, on Astei^olampra. 
the colour of the vaive^ even when mounted in balsam, 
brownish yellow. Two specimens only have occurred to me, 
in the Indian Ocean soundings. 
20. Asterolampra Sarcophagus. — " Valve oblong, with a 
slight constriction near each extremitj^ ; basal ray plane, and 
continuous with one of the true rays ; sutures plane ; cellules 
very large. Length -0018" ; breadth '0009'^'' 
Asteromphalus Sarcophagus, Wall., Trans. Mic. Soc, vol. viii, p. 47, 
pi. 2, fig. 12. 
Hab. — Indian Ocean, from Salpce, Dr. Wallich. 
As I have not had an opportunity of examining this very 
curious diatom, I give the specific character in Dr. Wallich^s 
own words. The form of the valve is so extreme a deviation 
from the otherwise more or less orbicular shape of the entire 
series, that an impression almost forces itself upon the mind 
that it is simply a malformation. Dr. Wallich does not men- 
tion how many individuals have come under his notice, but 
he has probably seen a sufficient number to satisfy him that 
its eccentricity of outline is permanent. It is most nearly 
related to A. Arachne ; for if we remove the terminal ray 
(which in many species may be either present or absent), the 
five remaining rays would occupy the relative position which 
they hold in that species, as well as the same direction ; one 
pair of perfect rays pointing upwards, the other pair down- 
wards. In both species also the areolation is large. 
Among several frustules of which I have only seen single 
specimens, and whose position is doubtful, is a minute and 
beautiful valve, of which I give a figure (fig. 20). It is 
allied to A. Hilioniana and A. flabellata, but cannot be 
satisfactorily referred to either. The lowest pair of umbilical 
lines are curved downwards, as in the former species. The 
median lines are parallel, and continued to the edge of the 
hyaline area, or, in other words, to the base of the median 
segments, in a decidedly square manner. The valve, at a first 
glance, is most conspicuous for the large size of the hyaline 
area and the consequently rapidly attenuated rays ; but this 
may prove to be a worthless distinction. It is only '00 18" in 
diameter. I shall not attempt a formal character, but it may 
bear, for the sake of convenience, the provisional name of A. 
stellata. It occurs in the Indian Ocean soundings. 
Asteromphalus centr aster, of Dr. C. Johnston, from Elide 
Guano (^Mic. Journ.,^ vol. viii, p. 12, PI. I, fig. 10). I can- 
not speak of with any certainty. The rays, in being con- 
tinued like distinct bars, or the ribs of an umbrella, from the 
central point to the margin, are unlike those of every known 
species of the group. There is evidently no true median ray . 
