372 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
Fig. 4. Rotalia turgida (Planulina? turgida), from the same locality, 
and equally magnified. 
a. Viewed from the right side. The colouring of all the cells, 
beginning with the second, by the prevalent ovarium, is likewise 
here evident. 
6. Outline view of the narrow surface in front. 
Fig. 5. Textilaria aciculata, in similar circumstances as the former, 
receat, and magnified to the same extent. 
a. Side view from the left. 
b. View of the narrow ridge in front, in outline. 
The two first chambers are, as in the Fotalie, the first only, and in 
Geoponus the four first, filled with colourless parts; the others are 
characterized by their coloured contents, which perfectly resemble the 
ovarium surrounding the intestinal canal of the other forms. 
PLATE VII. 
This and the following Plate contain twenty-two species of siliceous- 
shelled recent Infusoria of the Ocean, of which nine species have been 
recognised to be perfectly identical with the forms which constitute, 
by their innumerable quantity, the chalk marls of Sicily, Oran, Zante, 
and Greece. 
This third Plate contains, among six allied forms of the present 
world, five forms which likewise belong to the secondary formation — 
(fig. 1 to 5). 
Fig. 1. Coscinodiscus radiatus, the principal form of the polishing — 
slate of Oran and of the chalk marl of Caltanisetta, recent near Cux- 
haven, magnified 300 times. ‘ 
a. Broad lateral view. The cells are most directed in alternating — 
rows, radiately towards the centre; at the margin smaller, and in ~ 
the centre itself homogeneous and irregularly aggregated. In the 
centre of the dise is situated in the interior a green granulate body, — 
which is comparable to the ovarium of the Gallionelle. Marginal 
apertures are indicated in fig. d. 
b. The same, in outline, half turned. z 
c. The same, from the narrow side, where it is evident how each — 
two plano-convex shells form a single coin-like animal, as in Gal- 
lionella. 
d, A young specimen. 
It is to be observed, that the two specimens here figured are extremes — 
of the variation in form, the large one by its large, the small one by its — 
small acute-radiate cells. The first approaches closely to C. argus. | 
The natural specimens exhibit, by the arrangement of the cells, curved — 
lines varying on changing the light, which could not be represented — 
in the drawing. j 
Fig. 2. Coscinodiscus minor, a very frequent form of the chalk marl 
of Sicily, living, from Cuxhaven, magnified 300 times. 
a. Broad side. 
b. Front view of the narrow surface. 
c. Half turned (reverted). 
In the interior the ovarium is evident as a green mass. The remain- 
der of the inner soft body is transparent. 
a 
