Greville^ on New Diatoms. 
5 
same parts in the species above mentioned. It is seldom 
that a good view of the spine-like character of the ribs can 
be obtained ; but the disc now figured happened to be tilted 
up in such a way as to show it very conspicuously. 
ACTINOPTYCHUS. 
Actinoptychus minutus, n. sp., Grev. — Minute ; valve 
8-rayed ; the compartments alternately slightly raised and 
depressed, very minutely punctate ; umbilicus in the form 
of a minute cross^ with the ends truncate. Diameter '0017^'. 
(Fig. 13.) 
Hab. Monterey deposit; cabinet of L. Hardman^ Esq.; 
very rare. 
The smallest species of the genus,, with the surface nearly 
even, and the cellulation so minute as to justify the term 
punctate. 
Heliopelta. 
Heliopelta nitida, n. sp., Grev. — Disc with six compart- 
ments, the cellulate ones with 4 — 5 marginal spines ; central 
space obtusely hexagonal, containing a circular umbilicus; 
margin narrow, with a fine line running through it, and no 
perceptible striae. Diameter -0040''. (Fig. 18.) 
Hab. Deposit at Los Angelos, California; L. Hardman^ 
Esq. ; very rare. 
To my friend Mr. Laurence Hardman we are indebted for 
the discovery of what appears to be an unquestionably new 
species of this fine genus, and individually I have to thank 
him for enriching my cabinet with a specimen. Whatever 
view may be taken of the species described by Ehrenberg, the 
Californian disc difi:ers from all of them in the non -striate 
rim and in the well-defined non-stellate centre. The latter 
is an hexagonal umbilicus, containing a circular nucleus, and 
of a thicker and more opaque substance than the stellate 
central space in the other HeliopeltcB, The margin is rela- 
tively narrower^ and the cellules larger. 
EUPODISCUS. 
Eupodiscus minutus, n. sp.^ Grev. — Small ; disc slightly 
convex, obscurely cellulate, with four circular, submastoid 
processes, distinguished by a prominent lip on their marginal 
side. Diameter about '0020^^ (Fig. 13.) 
