Greville, on New Diatoms, 
49 
without any reference to the longer lines of granules^ or^ 
indeed^ to any lines at all. There is no umbilicus, but a few- 
irregular granules before the radiation commences. The lines 
are not crowded, and the shorter ones which come in to fill up 
the disc leave little open spaces. Towards the margin the 
lines suddenly disappear in a belt of close, minute, radiating 
puncta, in which the processes are situated, nineteen in 
number, on little roundish vacant spaces, as is often seen in 
the Aulacodisci. Diameter -0032'^ 
Cestodiscus (?) ovalis, n. sp., Grev. — Disc from broadly 
oval to narrow elliptical-oblong ; radiating granules spherical, 
passing into a crowded band of smaller granules, which is 
succeeded by fine striae and the circle of processes. (Fig. 9.) 
Hab, Moron deposit ; Rev. T. G. Stokes ; R. K. G. 
I have not been able to satisfy myself regarding the precise 
nature of the processes in this species. They are evidently 
not so like those of Aulaco discus as in the preceding diatom, but 
they are not spines. The disc is not furnished with a regular 
umbilicus, although there is often a small, irregular, blank 
space. The granules radiate very irregularly, and terminate 
suddenly at the commencement of the band of the smaller 
ones. The latter form an uneven outer line, from whence the 
fine striae are continued to the margin. The number of pro- 
cesses is about twelve or fourteen. In size and relative pro- 
portion the disc varies greatly, being sometimes quite narrow. 
The specimen figured is a very fine one, '0030'' in length. In 
order to bring out the characters more clearly I have magni- 
fied both the species of this genus 600 diameters. 
BiDDULPHIA. 
Biddulphiu sinuata, n. sp., Grev. — Valve very minutely 
punctate, sinuate, with a two-lobed median elevation and a 
group of spines in the centre of each lobe j processes rather 
long, capitate. (Fig. 10.) 
Hab, Bardadoes deposit, Cambridge estate; extremely 
rare. 
Unfortunately the only part of the frustule which I have 
seen is the valve, which, however, is of the chief importance, 
and in the present instance affords such valid characters that 
no doubt can be entertained on the subject of the diagnosis. 
It is manifest at a glance that the species it most closely 
approaches is B. pulchella ; but its affinity lies only in the 
contour of the valve. The differences are remarkable and 
instructive, showing how very nearly one species may resemble 
another in one aspect, while in every other it is removed to a 
