20 
GiiEviLLE^ on New Diatoms. 
can be no doubt about their true nature. Besides the proper 
continuations^, there are sometimes short, supplementary ones, 
which do not answer to any of those exterior to the median 
space, as well as lines of puncta (see the figure) which must 
be regarded as abortive supplementary costse. 
The late Professor Gregory had observed, as he believed, inter- 
mediate states between this species and S. lata. Such speci- 
mens have not occurred to myself. I may mention, however, 
that the structure of the middle portion of the disc is very 
similar in both species. Nothing definite is conveyed by the 
figure of S. lata in Smithes synopsis with reference to this 
part. The median space in that species, as well as in 
S. fastuosa, is not itself striated, but is bounded on each side 
by a line of exceedingly short striae, which apparently form a 
narrow ridge. A difference, however, exists in the shape of 
the median space ; the normal form of that of S. lata being 
linear, or, at least, having parallel sides, while that of 
>S. fastuosa is lanceolate. And although in the latter it not 
unfrequently becomes linear, I have never seen it expand 
into lanceolate in the former. In both species, when the 
median space is narrow, there are no central continuations 
of the costse, but when the space is broad these occur in 
<S. lata as well as in B. fastuosa. 
Surirella Macraeana, n. sp., Grev. — Oblong, constricted in 
the middle, with broadly rounded ends and narrow median 
area, enclosed within two lines of punctiform striae; costal 
distant, externally dilated, the dilated portion transversely 
punctate. Lengtli -0072''. (PL II, fig. 1.) 
Hab. Ceylon, Dr. Macrae. 
A very remarkable diatom, distinguished pre-eminently by 
having the dilated portion of the costse coarsely punctate. 
At first sight they appear to be transversely barred, but 
careful adjustment brings out the transverse puncta. The 
general outline of the frustule resembles that of S. lata, as 
figured in the ^ Synopsis of the British Diatomacese.' The 
lines which enclose the narrow median space are composed 
of what should be considered normally striae, but these 
are exceedingly short, and often nothing more than 
puncta. 
Campylodiscus. 
Campylodisciis biaagulatus, n. sp., Grev. — Disc nearly 
circular, with a bi'oadly linear, smooth, median space, ex- 
tending at each end nearly to the margin ; surface waved so 
as to produce an angular, converging line between the median 
