14 
Greville^ on New Diatoms. 
This most graceful species in some respects closely re- 
sembles my Campylodiscus Normanianus. The form of the 
central space is precisely similar, and the number of the 
canaliculi is about the same. It is, however, a much more 
delicate species. The canaliculi are far more slender ; indeed_, 
the sharpness and fineness of the lines are most striking at 
the first glance. Dr. Wallich correctly remarks, in his notes 
upon his St. Helena dredgings, which he has most kindly 
placed in my hands, that the canaliculi, when seen in a favor- 
able point of view, exhibit themselves as the angular edge of 
elevated ridges. In an accurate sketch by him, now before 
me, the canaliculi pass quite across the central space, closely 
and very minutely beset with spinulse; I have also seen a 
similar specimen from New Caledonia, but it is an excep- 
tional case, as they rarely traverse more than a third of the 
distance, and often not so much. The irregularity, however, 
of the central markings in this genus are now too well known 
to have any influence over specific diagnosis. 
Campylodiscus Robertsianus, n. sp., Grev. — Valve circular, 
with an oval central space and prominent radiating costse 
of equal length, the ridge of which is composed of minute, 
oblong cellules, in pairs. Diameter '0050'^ (Fig. 5.) 
Hab. Harvey Bay, Queensland ; Dr. Roberts. 
One of the most exquisite species of this charming genus. 
The valve is bent and concave. The costse or canaliculi re- 
semble sharply prominent ribs, along the crest of which are 
disposed longitudinally numerous minute, oblong cellules, in 
pairs, which in some lights might be hastily taken for short 
lines. The nearest ally of this remarkable species is unques- 
tionably C. diplostichus, also a native of the Australian seas, 
where it was obtained from the stomachs of Ascidians by Dr. 
Macdonald. I am indebted to the kindness of Dr. Roberts, 
of Sydney, for a series of gatherings from the Southern 
Pacific, which, having very recently arrived, are mostly un- 
examined. I rejoice, however, in having an early opportunity 
of dedicating so well-marked a species to Dr. Roberts, who, 
from want of leisure, has been prevented from carrying out 
his intention of investigating the Diatomacese of the Southern 
Ocean. 
Campylodiscus crebrecostatus, n. sp., Grev. — Valve nearly 
circular ; canaliculi imperfectly radiating, very numerous, 6 
in '001", forming a broad, marginal band, the outer portion 
being bent back, so as to form a ridge along the middle of 
the band; central space elliptical, closely filled with fine 
transverse costse, interrupted by a narrow median line of 
blank space. Longest diameter •0037". (Fig. 6.) 
