356 THE MEDALS OF CREATION. Cuar. Xa 
as in the sketches Lign. 114, ante p. 351. If a chip or 
slice of flint, rendered transparent by immersion in oil of 
turpentine or Canada bal- 
low power, (1 inch object 
glass,) to discover a good 
specimen, and afterwards 
or an + object glass,) the 
8 
form of the shell and of the 
as in Lign. 116. In this 
Lien. 116. segments are as sharply de- 
SECTION OF A ROTALIA IN FLINT. fined as in a recent example: 
(Seen by transmitted light, and showing and one of the cells (a) is 
beautiful fossil Rotalia, the — 
sam, be viewed first with a — 
under a high magnifier, (a+ — 
cells will be distinctly seen, — 
the chambers partially filled with mine- seen to be lined with quartz : 
ral matter.) 
crystals. 
At first sight this fossil 
might be mistaken for anau- 
tilus partially filled with spar ; but the reader will remark that 
a. A cell lined with spar. 
(x 250 diameters.) 
the septa, or partitions, have their convex surface towards — 
the aperture ; whereas in the shells of the Cephalopoda — 
(Nautilus, Ammonite, &c.) the septa are concave anteriorly. — 
In Lign. 114, fig. 4, a series of casts in flint of the — 
septa of a young Nautilus is represented ; by comparing it 
with the Rotaliz in the same lignograph, jigs. 2, 3, this dis- 
tinction will be obvious. And here it may be necessary 
again to point out the essential character of the animal of 
the foraminifera, as distinguished from that of the cephalo- 
poda with chambered shells. In the latter, the body of the 
mollusk only occupies the large outer chamber ; the internal 
compartments are empty dwellings, which the animal has 
successively quitted in the progress of its growth, and with 
which it has no connexion except by the siphunculus, In 
