Greville^ on Asterolampra. 
123 
be inferred with some degree of confidence^ that it is an 
important character when met with in other species. Little 
spine-like processes are seen to project from the angles in 
several allied forms^ and may be the basis of similar ramuli. 
In the diatom under consideration^ the base of each ramulus 
is conspicuous^ but it appears at first sight to stop abruptly, 
and it requires very careful adjustment to trace the fine con- 
tinuation to the angle of the segments. In other species_, 
while the spine-like base is sufficiently obvious, the very 
delicate continuation may escape observation altogether. The 
colour of the valve is very pale yellow ; the areolation larger 
than in any other member of the group. 
19. Asterolampra Arachne. — Valve broadly ovate ; hyaline 
area very small and eccentrical ; areolated segments curved 
at the base, the upper one very widely, the lateral ones 
sharply; umbilical lines two, lateral; median lines dilated 
upwards ; rays five, the two superior ones curved upwards, 
widely apart. Diameter about '0021". 
Spatanidium Arachne, De Breb., Bull. Soc. Linn, de Normand., vol. iii, 
pL 3, fig. 1. 
Asteromphalus malleus, Wall., Trans. Mic. Soc, vol. viii, p. 47, pi. 2, 
fig. 11. 
Hah. — Peruvian Guano, De Brebisson. In Salpa, Indian 
Ocean, Dr. Wallich. Indian Ocean, in soundings at 2200 
fathoms, made by Captain PuUen. 
It would be fortunate for the student if diatoms were in 
general as faithful to their characters as this remarkable 
species. It is one of the few belonging to the present group, 
of which it may be said that the number of rays is really 
constant. Their disposition is also very peculiar. The hya- 
line area is so small as scarcely to be perceived at first sight, 
being composed merely of the very short suddenly dilated 
bases of the four perfect rays and the space enclosed within 
the short median lines. The rays are attached to the sides of 
the median lines, nearly the whole of which they occupy. 
The upper pair turn their backs, as it were, on the lower pair, 
curving outwards and upwards, and bear much the same rela- 
tion to the median lines as the horns of an ox do to the frontal 
bone. The lower pair of rays are straight, and point laterally 
downwards, forming a group of three with the median ray. 
The median lines also exhibit a character peculiar, I believe, 
to this species, in not being united at the top ; they do not 
even incline towards each other, but stop abruptly, leaving 
the intervening space in juxtaposition with the base of the 
upper areolated segment. Another anomaly occurs in this 
part of the valve, in the segment just mentioned being un- 
supported by an umbilical line. The areolation is large ; and 
