THE AMERICAN MIDLAND .NATURALIST 45 
very pleasant and extensive correspondence with these last three 
named gentlemen many problems have been solved and all novel- 
ties and changes have passed through their censorship. 
In order to elucidate the refetences in the text made to the 
physiography and geography an excerpt of the geographic distri- 
bution and also a tabulated Account of the Mussel Faunae of 
Missouri are given here, although, when it is possible to secure 
the desired data, it is the intention of the author to give a detailed 
account of the zoogeography of the Naiates of Missouri and atljacent 
territory in relation to the restoration of the ancient geographic condi- 
tions of Central Mississippi Valley. 
In this connection the hydrography of the State may also be 
given for the sake of clearness in the use of the text. The drainage 
to the Mississippi is mostly through the Missouri River which 
flows entirely across the State just above the central line, and, 
because of the loess soil held in suspension, together with its 
shifting sand bars and mud beds, it forms ‘a great faunal 
barrier.”’ Hence we may account for such a distinct mussel fauna 
north of the Missouri (known as “Old Muddy’’) from that south 
of it. The depauperization of mussel life is remarkable as noted 
in this river, together with that of the Mississippi from the mouth 
of the Missouri to a point below the southern boundary line of 
the State. The chief river basins of North Missouri belonging 
directly to this faunal barrier are the Chariton, the Grand, the 
Platte, the Nodaway and other minor ones of the Northwest. 
A chain of lakes, formed by the changing of the Missouri River 
channel into ‘“‘ox-bow cut-offs,” are found mostly in the north- 
western part of the State along the Missouri in its eastern and 
northern flood-plains. The largest river basins draining into the 
Missouri River from the south are the Osage, Gasconade and 
Black-water. The most important one which drains directly into 
the Mississippi from this State is the Meramec. The chief basins 
found on the south slope of the Ozarks are the White, Black and 
St. Francis Rivers which are drained into the Mississippi through 
Arkansas. South-west Missouri drains into the Mississippi River 
partly and directly through the Neosho. 
The following is a Classified Account, (although apparently 
contrary to the geologic facts, yet self-explanatory), showing the 
distinct mussel faunae of the State that coincide with the different 
