198 TRANS. OF THE ACAD. OF SCIENCE. 
ancestors of New Fossts or se Coal Measures of 
Missouri and Ke 
BY B. F. SHUMARD AND &G. C. SWALLOW. 
-Navritvs Missovrrensis, Swallow. 
. small, gibbous, smooth, somewhat flattened on the 
margin ; pees reniform, transverse, slightly modi- 
edb: orl; septa sparingly seas a margin 
curved a little forward tow acts the inner border of the shell; 
si; € sub-central, a little nearer the anol margin; : 
wbitious leep, y close oc 
- Tore ;* thickness of last whorl, 0. 54: diameter of 4 
3 a 
