474 
VERTEBRATES. 
The river vertebrates observed were as follows: 
Rana pipiens. Leopard-frog. 
Chrysemys marginata. Western Painted Tortoise. 
Ameiurus melas. Black Bullhead. 
STATION XXII. 
In many places the river forms bayous of considerable depth, 
which are largely filled with Iris versicolor. This area, as well as 
certain portions of the flood-plain adjacent to the river, is subject to 
overflow. Physa and Planorbis are abundant in this habitat, and 
Lymnea parva sterkii is common on the margin on leaves and sticks, 
or on the bare surface of the mud. It is seldom found in the water. 
MOLLUSKS. 
Physa gyrina. 
Planorbts trivolvis. 
Lymnea parva sterku. 
STATION XXIII. 
Small streams running into river,on west bank. These streams 
start from springs in the higher ground and gradually enlarge until, 
in several cases, a stream has been formed two or three feet in width. 
That there is frequently a large volume of water is shown by the 
depth to which the stream has cut, forming a miniature valley, 
and cutting away a large portion of the surrounding area. In the 
summer and fall these streams completely dry up. The banks on 
the west side of the river are more heavily wooded, thereby holding 
the water and storing it up in springs. 
Physa gyrina was the only mollusk found in these streams. 
STATION XXIV. 
(Plate XIX.) 
The flood-plain between the river and the terrace-like banks. 
The ground is low and level, and subject more or less to overflow 
from the river during high water. The vegetation is made up of 
two main plant societies—(1) the trees which have descended from 
the terraced banks and (2) the more natural semiaquatic vegeta- 
tion. The notable species of each group are as follows. 
