Greville^ on Asterolampra. 
109 
with tlie frustules '^^ moderately abimdaut/^ not one should 
have been observed having other than seven or eleven rays. 
The extreme range appears to be from six to twelve ; Dr. 
Waliich refers to one in his possession^ without mentioning 
the locality, containing the latter extraordinary number. It 
is, however, now admitted on all hands that the number of 
rays is of no diagnostic value whatever ; and, consequently, it 
is necessary to bring together all those so-called species which 
have no other character to rest upon. Among the examples 
which I have given in Plate III, are frustules with six, seven, 
and nine rays ; but I have not selected these forms on account 
of this variation, but in order to show how widely the valves 
may otherwise differ, and to assist in determining the ques- 
tion of identity. In fig. 1, from Piscataway, Maryland, the 
rays are not only numerous, but the segments form an ex- 
tremely deep curve ; and in Dr. Wallich^s figure, 14, 1. c, 
the same effect is produced with fewer rays, in consequence 
of the segments being carried still nearer to the umbilicus. 
In my figure 3, detected by Mr. Dallas in " Bermuda Tripoli,^' 
the species seems to have reached the very opposite extreme, 
and its most aberrant condition. The hyaline area is so large 
as to occupy half the radius ; and the curve of the areolated 
segments is not only very shallow, but ceases to be regular, 
being considerably flattened; all which makes the rays appear 
so short, that they might be compared to the handles of a 
steering-wheel. I have introduced figure 2, from Rappahan- 
nock, to show that while the hyaline area occupies even a 
larger portion of the valve than the preceding, the segments 
preserve the true curve. The valve has seven rays, and pre- 
sents a most striking contrast to Dr. Wallich^s fig. 14, 1. c. 
My fig. 4 represents a frustule from the Indian Ocean sound- 
ings, remarkable for its gigantic size. It exhibits also a pecu- 
liarity, observable in all the specimens, obtained from the 
same quarter, — a greater breadth of the ray than usual. The 
umbilical lines may be said to be normally simple in this 
species ; but one or two of them are occasionally forked close 
to the central point, as seen in fig. 1. 
With regard to the nature of these lines, it is improbable 
that they indicate an actual division or dissepiment between 
the bases of the rays, as such a provision would seem to be 
useless while the remaining portion of those organs is so 
firmly united to the adjoining parts. In the numerous frac- 
tured specimens of Asterolampra and Spatangidium I have 
examined, I have never been able to trace any disposition in 
the valve to break up in the direction of these lines. The 
more correct view, it appears to me, is that suggested by Mr. 
