26 THE AMERICAN MIDLAND NATURALIST 



NAIADGEOGRAPHY OF MISSOURI. 



BY \V. I. UTTERBACK. 



The writer would presume to use the term, Naladgeography, 

 because it is a convenient and comprehensive expression for "the 

 geographic distribution of the Naiades, or Fresh-water mussels." 

 This coined term is employed here to correspond with that one in 

 good accepted usage, that is, ZOOGEOGRAPHY. However, the latter 

 term is less specific, having reference to "the geographic distri- 

 bution of animals generally." 



After some years of study of the Xaiadcs of Missouri the 

 writer has In en able to work out a key to the mussel faunae 

 which may be used as a summarized account to precede the tabu- 

 lated list on NAIADGEOGRAPHY. 



I. — PRAIRIK DRAINAGE. Naiadgeogkaphy: — (Ecology: — Streams 

 sluggish, turbid, mud bottom); (Coincidental Morphology: — 

 Shells mostly large, smooth, inflated). 

 i.— NORTH MISSOURI FAUNA. — Missouri R. Southern Boun- 

 dry. Physiography: — Level or rolling plains with lower stream 

 conditions; Coincidental Characters: — Mussels scarce, mostly 

 lacustrine. 



a.— NEW PRAIRIES, OR GLACIAL PLAINS. 

 ai. — MISSOURI RIVER FLOOD PLAINS (Depauperated 

 Mussel Fauna). 

 2.— CENTRAL MISSOURI FA UNA . — Missouri R. Northern 

 Boundry. Physiography:— Intermediate Topography and Hy- 

 drography; Coincidental Characters: Mussels fairly abundant, 

 primitive-modem . 

 II.— OZARK DRAINAGE. Naiadgeography. (Ecology: — Streamsswift, 

 clear, rock bottom); (Coincidental Morphology: — Shells mostly 

 small, rough, compressed). 

 2.— CENTRAL MISSOURI FAUNA. Ozark Crest Southern 

 Boundry. 

 a. — Ozark Border (Lower Osage). 

 b. — Ozark Plateau (Gasconade Basin), 

 c. — Ozark Center (Meramec Basin). 

 3.— SOUTH MISSOURI FA UNA ,— Southern Slope of the Ozark 

 Uplift. Physiography:— Dissected Uplift with upper steam 

 conditions; Coincidental Characters: Mussels abundant, modem 

 mostly fluviatile. 

 a. — Ozark Border (S. W. Mo., Neosho Basin), 

 b. — Ozark Plateau (White River Basin), 

 c. — Ozark Center (Black River Basin). 



