1893.] Mollusks of Louisiana. 947 
for the growth of the shells easily accounts for this. Bulimulus 
dealbatus and Helicina orbiculata were found in abundance only 
on these soils. 
All of the chief streams, large bayous, as well as rivers, flow 
in a general southerly direction. The two main streams are 
Red River and Ouachita River. “A dividing ridge, frequently 
noticeable only on closest inspection, runs almost central be- 
tween the rivers, dividing the Ouachita and Red River system 
eastward and westward” (Lerch). Thus, certain of the bayous 
flow into Ouachita River, such as Cypress and Corney, and 
others flow into Red River, such as Dorcheat, Black Lake 
Bayou, Bayou Bodeau, etc. Bayou Pierre is on the west side 
of Red River. 
One of the most noteworthy things about these streams is 
that they are subject to great periodical overflows. "Thus, in 
the summer of 1891, I remember rolling up my trousers to my 
knees and wading across Bayou Dorcheat, but in the spring of 
the following year, when Red River was so overflowed as to 
wash away much of the railroad track, steamboats took passen- 
gers down the Dorcheat and up Red River to Shreveport. 
Another feature of Red River is the flat, basin-like reser- 
voirs, called lakes, that are found on either side of it. In 
many cases it is impossible to find any banks to these lakes, so 
gradually does the land slope toward them. There isa stream 
always flowing through the middle of them, and, in conse- 
quence of an insufficient outlet, the water accumulates at the 
lower portion of thestream. The high water in these lakes is 
caused either by back-water from the river, or by a large 
amount of water being brought by the stream that opens into 
them. 
The bottoms or beds of these lakes and bayous are usually 
very soft, and collecting is thus rendered abominable, it often 
being a continuous process of wallowing in the mud. Some- 
times a firm foundation may be found to stand on, but it isthe 
exception. In Red River one usually sinks waist-deep in the 
soft mud. The bottom of the smaller creeks is usually some- 
what firm. 'The small ereeks in the sandy hills of the long 
leaf pine region have beautiful, firm, white sand bottoms, and 
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