U2 
Greville, on New Diatoms. 
striae are 16 in '001'', and form a narrow marginal band. 
There is a remarkable angularity and squareness in the 
whole aspect of this diatom. Length about '0040'^ 
Gephyria. 
Gephyria gigantea, n. sp., Grev. — Valves much elongated,, 
broadly cuneate and obtuse at the ends; costse about 3^ in -001"' 
(Figs. 7, 8.) 
Hab. Monterey deposit, California ; Laurence Hardman, 
Esq. 
A truly magnificent species. A lower valve now before 
me measures -0120'^ in length! A smaller example is 'OlOO'', in 
which the breadth is '001 7'^ in the middle. Towards the ends 
the valve dilates a little, and then becomes broadly cuneate 
or elliptic-cuneate. Compared with this species, all those 
previously described are as dwarfs. In the' largest of them 
(G. incurvata) the costse of the valve are about 7 in 'OOl'', in 
the one now described they are only 3^ in 'OOl'". 
Omphalopelta. 
Omphalopelta Moronensis, n. sp., Grev. — Small; disc with 
six compartments, filled with decussating striae variously 
arranged, causing a play of colour ; three of them pale, with 
a deltoid impression, the others darker, with a sort of trira- 
diating nucleus and a marginal spinous process. Diameter 
•0030'^ (Fig. 14.) 
Hab. Moron deposit, Province of Seville ; Laurence 
Hardman, Esq. ; extremely rare. 
An exquisite little diatom, the markings of which cannot 
be satisfactorily reproduced by the artist, as they depend for 
effect upon the slightest change of focus. I have endeavoured 
to delineate what may be regarded as the most peculiar 
aspect. The play of colour is somewhat similar to that seen 
in 0. versicolor, only not so brilliant. This effect seems to 
arise, not alone from the outer pellicle, the striae of which 
are uniformly decussate, but partly from the undulation of 
the surface, and possibly from the subjacent structure. The 
marginal processes do not occur in all the compartments in 
accordance with the generic character, but only in the alternate 
darker ones. At the same time the diatom is too closely 
allied to O. versicolor to admit of its being removed. The 
presence or absence of spines, in many cases, at least, does 
not appear to be of much importance. 
