58 
ELEMENTS OF GEOLOGY. 
state. The annexed figure (Fig. 47) represents a branch 
of one of many new species found by Professor Amici in 
the lakes of Northern Italy. The seed-vessel in this plant 
is more globular than in the British Charce^ and therefore 
more nearly resembles in form the extinct fossil species 
found in England, France, and other countries. The stems, 
as well as the seed-vessels, of these plants occur both in 
modern shell-marl and in ancient fresh-water formations. 
They are generally composed of a large central tube sur- 
Fig. 46. 
Chara medicaginula ; 
fossil. Upper Eocene, 
Isle of Wight. 
a. Seed-vessel magnified 
20 diameters. 
h. Stem, magnified. 
Fig. 4T. 
a. Sessile seed-vessel between the divisions 
of the leaves of the female plant. 
V. Magnified transverse section of a branch, 
with five seed-vessels, seen from below 
upward. 
rounded by smaller ones; the whole stem being divided at 
certain intervals by transverse partitions or joints. (See 
b, Fig. 46.) 
It is not uncommon to meet with layers of vegetable mat¬ 
ter, impressions of leaves, and branches of trees, in strata 
containing fresh-water shells; and we also find occasionally 
the teeth and bones of land quadrupeds, of species now un¬ 
known. The manner in which such remains are occasional¬ 
ly carried by rivers into lakes, especially during floods, has 
been fully treated of in the “ Principles of Geology.” 
Tresh-water and Marine Pish. —The remains of fish are oc¬ 
casionally useful in determining the fresh-water origin of 
strata. Certain genera, such as carp, perch, pike, and loach 
{Cyprimis^ Perca^ Esox^ and CoMtis)^ as also Lebias^ being 
peculiar to fresh water. Other genera contain some fresh¬ 
water and some marine species, as Coitus^ Mugil^ and An¬ 
guilla^ or eel. The rest are either common to rivers and the 
sea, as the salmon; or are exclusively characteristic of salt 
water. The above observations respecting fossil fishes are 
applicable only to the more modern or tertiary deposits; 
