Greville^ on New Diatoms. 
79 
conspicuous, for it does not appear to be ever circular or even 
to approach towards it, but ranges between a true oval and 
elliptic-oblong. There is no umbilicus, but a loose irregular 
cluster of large, round granules, radiating in either slightly 
curved or straight lines to each end, diminishing gradually in 
size ; the lines are so wide apart that four to seven fill up the 
space, and leave but little room for the few very short lines 
which radiate to the sides. Just within the striated margin 
is a very narrow belt of minute puncta. 
Craspedodiscus. 
Craspedodiscus umbonatus, n. sp.— Disc hexagonally cellu- 
late, the border nearly equal to half the radius, the centre 
rather sharply umbonate. Diameter, '0035''. (Fig. 15.) 
Hab. Barbadoes deposit, Cambridge estate; in slides com- 
municated by C. Johnson, Esq. 
Distinguished at once by its umbonate centre. Cellules 
near the margin of the border 8 in -OOl"". 
CoSMIODISCUSj ?2. 
Frustules simple discoid ; disc radiato-punctate or cellu- 
late, with linear, blank radiating spaces extending from the 
margin inw^ards (no processes nor internal septa). 
Whether the three diatoms I have here brought together 
are really generically allied I will not, in the present state 
of our knowledge regarding them, take upon myself to say. 
As, however, they agree in the most prominent character, a 
provisional union will be, at least, convenient. The genus is 
constructed specially for the disc first described, which for 
many years has perplexed me w^hen called upon to examine 
the Monterey deposit. All these discs appear to be allied to 
Aulacodiscus , in having blank lines or channels radiating 
through more or less of their surface towards the margin ; 
but being destitute of lateral processes they must be arranged 
among the Cosciiiodiscea. 
Cosmiodiscus elegans, n. sp., Grev. — Disc with a broad, 
smooth margin, and numerous very narrow radiating blank 
lines; intervening compartments filled wdth very minute 
puncta passing into strise next the margin. Diameter, -0035''. 
(Fig. 13.) 
Hab. Monterey deposit; L. Hardman, Esq.; R. K. G. 
Disc with an irregular, blank umbilicus ; granules minute, 
somewhat scattered and irregularly arranged for some dis- 
