94 
GrevillEj 071 New Diatoms. 
with nearly straight sides and very rounded angles ; surfac. 
covered with lines of very minute dots, radiating from the 
centre in variously curved fasciculi to the margin, which is 
composed of a very narrow blank space. Striae about 20 in 
•001". Diameter between the angles '0024". (Fig. 9.) 
Hab. Indian Ocean soundings in 2200 fathoms, made by 
Captain Pullen. 
A delicate neat-looking species, very similar in outline to 
T. obscurum, of my Series IIT, but the striae are much more 
minute, and arranged in curved fasciculi of eight or nine or more 
rows, which follow no apparent plan of arrangement. These 
curved bundles of strise are so decidedly marked as to remind 
the observer of the (more uniform) arrangement in Coscino- 
discus subtilis. It does not approach in any degree, in the 
curvation of the striae, to T. condecoruni. 
Triceratium inornatum, n. sp., Grev. — Minute ; valve with 
slightly concave sides and rounded angles, the whole surface 
covered with short, imperfectly radiating lines of very minute 
dots pointing in all directions, about 20 in "OOl". Diameter 
between the angles -0017" to -0024". (Fig. 10.) 
Hab. Indian Ocean soundings in 2200 fathoms, made by 
Captain Pullen. 
The most noticeable feature in this little unattractive species 
is the equal distribution of the minute, dot-like cellules over 
the entire surface, and their arrangement, by which the lines 
are broken up, as it were, into short bundles, which cross 
each other in all directions. Towards the margin they 
radiate more regularly. The margin itself appears to be 
composed of a delicate double line, which passes round the 
angles. 
Amphitetras. 
Amphitetras producta, n. sp., Grev. — Lateral view, with 
the sides nearly straight ; angles rounded, produced, contain- 
ing conspicuous apparent openings ; cellulation minute, radi- 
ating in distinct lines from the centre ; the lines at the margin 
10 in -001". Diameter between the angles about '0020". 
(Fig. 11.) 
Hab. Manilla ; obtained from shell-scrapings. George 
Mansfield Browne, Esq. Dredged oflP St. Helena; Dr.Wallich. 
All the specimens I have examined of this small species 
agree exactly with each other. The most remarkable feature 
about it consists in the angles, which have the appearance of 
being double. Beyond the primary boundary of the valve^ a 
supplementary projection is added, and in the small space so 
enclosed the apparent opening is situated. 
