77 
Descriptions o/New and Eare Diatoms. Series J5Z3^ 
By R. K. Greville, LL.D., F.E.S.E., &c. / 
Plagiogramma orientale, n. sp., Grev.-— Minute j valve 
panduriform^ with central costse and shortly produced apices ; 
puncta very minute, impervious decussating lines. Lengthy 
•0012". (PL VIII, fig. 1.) 
Hab. Zanzibar; Professor Hamilton. L. Smith. 
Almost as minute as P. atomus, and resembles it in form, 
only not so deeply constricted. The chief difference, how- 
ever, lies in the absence of costse at the ends. 
Gephyna constrictaj n. sp., Grev. — V alve with obtuse, cre- 
nate ends, and deeply constricted in the middle ; costse 5—6 
in -001". Length, -0055" to -0072^ (Fig. 2.) 
Hab. Monterey deposit; L. Hardman, Esq. 
A noble species, of which, through the kindness of Mr. 
Hardman, I have seen a number of examples. The constric- 
tion is so remarkable that, while the widest part of the 
frustule is nearly -0020'^, it is often only -0007'" across the 
middle. The relative proportion, however, of the two parts 
varies to some extent. Between the costse the valve has a 
minutely punctate appearance ; but on a careful examination 
this seems to arise from a subjacent very minute cellulation. 
In Mr. Hardman^s cabinet is the front view of a lower valve 
of a gigantic Gephyria, nearly '0120'' in length ; in which 
the base of the valve is punctato-striate. 
Melosira costata, n. sp., Grev. — Pale ; joints cylindrical, 
uninterrupted, longitudinally costate. Breadth of filament, 
•0003" to -0007". (Figs. 3—6.) 
Melosira ? — Small form with longitudinal markings, Nor- 
man, in ' Annals of Nat. Hist.,^ vol. xx. 2nd Series, p. 159. 
(1857.)-^ 
* ' Notes on Diatomacese from the Stomach of Ascidese/ By George 
Norman, Esq. 
(Communicated by C. S. Ropee, T.L.S., &c.) 
(Read March 14th, 1866.) * / 
Plagiogramma. 
Gephyria. 
Melosira. 
