46 
GrevillEj on New Diatoms. 
be readily taken for the other. Bat a closer examination 
shows that, apart from the spines, the irregularity of the 
outer row of cellules is characteristic of the Coscinodiscus, as 
also the much narrower margin. The diameter is variable, 
but fine examples, like the one figured, are about '0050.'' 
Number of cellules scarcely 4 in '001'' 
Coscinodiscus Macraeanus,n. sp.,Grev.— Disc large, slightly 
convex, with large, equal, hexagonal cellules, and with a broad 
hyaline border, having a narrow line next the cellules, giving 
off remote, radiating, clavate processes. (Fig. 4.) 
Hab. Indian ocean j Dr. Macrae. 
In size this fine species is equal to the last, while the cel- 
lulation is somewhat smaller. As in the preceding also, the 
cellules being regularly hexagonal, there is no radiant ar- 
rangement, the structure resembling a uniform piece of net- 
work. The characteristic feature of the species lies in the 
row of brilliant, coloured, clavate processes given off by a 
narrow line which constitutes the boundary of the cellula- 
tion. Diameter of disc -0050''. Cellules 5 in -001''. 
PORODISCUS. 
Porodiscus splendiduSy n. sp., Grev. — Disc circular (occa- 
sionally broadly oval), very convex, with a large umbilical 
pseudo-opening; structure a radiating reticulate cellulation. 
(Fig. 5.) 
Hab. Barbadoes deposit, Springfield estate ; Laurence 
Hardman, Esq. 
One of the finest species of the genus, distinguished at 
once by the larger and . more lax cellulation. It is remark- 
able that it should never have occurred in specimens of the 
deposit brought from the Cambridge estate, in which all the 
other species have occasionally been found. P. oblongus 
is common to both, though chiefly associated with our present 
new species. The diameter of the disc is 0030'^ Radiating 
cellules about 8 in -001'^ 
I take the present opportunity of stating that I have re- 
cently met with several discs of Porodiscus major {' Trans. 
Mic. Soc.,^ Vol. XI), all more or less imperfect, but which 
show the size to be not less than '0045'' in diameter. The 
pseudo-opening varies in size, and so does the degree of 
sparseness of the granules in the central portion of the disc. 
I beg to offer the following amended character : 
P. major ; disc circular, very large and convex; the ra- 
diating puncta very minute, brilliant, more or less remote 
for some distance round the pseudo-opening, afterwards 
