GREVILLE, ON DIATOMACEZ. 161 
nucleal line, contributes to give the “subpinnate” character 
to the four pairs of lateral rays which De Brébisson has 
noticed; but we must keep in mind that, if instead of the 
short middle ray, two were introduced, as in figs. 4 and 5, 
the subpinnate character would be lost. 
A. elegans, n. sp., Grev.—Radiating lines of the hyaline 
area with an angular bend in the middle, and inserted on the 
end and sides of the nucleal line; diameter of disc -0030’. 
(Fig. 6.) 
In Californian guano. 
I have only seen one example of this most beautiful spe- 
cies. It is very nearly, though not quite perfectly orbicular, 
and the hyaline area is almost centrical. The rays, thirteen 
in number, are equidistant. As, however, all these features 
are liable to variation, I have not introduced any of them 
into the specific character. 
Spatancipum, Bréb. 
It is with no trifling degree of hesitation that I venture to 
dissent, in some measure, from so eminent an authority as 
De Brébisson ; and it will afford me much satisfaction if, on 
a revision of the subject, he shall approve of the manner in 
which I have modified his genus. 
SpaTancipum, Bréb.—Frustules simple, two-valved, disci- 
form, distinctly areolated; the valves marked with rays pro- 
ceeding from an excentric hyaline area, the median ray very 
narrow. 
In this genus I retain S. Arachne and S. heptactis of De 
Brébisson, both having a distinctly areolated structure. The 
former has a broadly ovate form, the rays five, and very 
excentric ; the latter, according to De Brébisson’s figure, 
beirg slightly larger, more orbicular, but still somewhat ovate, 
with seven rays, ‘‘ subarcuatis obtusis,”’ which are as decidedly 
excentric as those of the other species. 
I have now to describe an additional species of great 
beauty which I find not unfrequently in Californian guano ; 
it has also been obtained from Peruvian (Bolivian) guano by 
Mr. George Norman, and it also exists in slides of Peruvian 
guano kindly communicated by Professor Walker-Arnott. 
Mr. Norman having named it in MS. in honour of our 
mutual friend Mr. Ralfs, I gladly give him due precedence. 
S. Ralfsianum, n. sp., Norman.—Greatest diameter of the 
