GASTEROPODS. 137 



above, broadly rounded below ; peripheral margin elevated 

 above the suture, which is strongly defined ; umbilicus small. 

 Aperture large, subquadrate. Surface smooth, marked by 

 small regular lines of growth. 



Horizon and localities Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



Pleurotomaria valvatiformis MKBK & WORTBEN. 



Pleurotomaria valvatiformis Meek & Worthen, 1866 : Proc. Acad. Nat. Sci., 



Phila., p. 273. 

 Pleurotomaria valvatiformis Meek & Worthen, 1873: Geol. Sur. Illinois, 



vol. V, p. 602, pi. xxix, figs. 9a-b. 

 Pleurotomaria valvattformis Keyes, 1891: Proc. Acad. Nat. Sci., Phila., 



p. 254. 



Shell very small, about twice as wide as long. Whorls 

 about four in number, rather rapidly increasing in size; very 

 regularly convex; suture deep; umbilicus minute; aperture 

 circular in outline, flattened somewhat on the inner side; sur- 

 face marked by fine revolving lines. 



Horizon and localities Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



The form under consideration is the smallest of the group 

 yet observed in the Mississippi basin. The species has a much 

 wider geographic distribution than has hitherto been sus- 

 pected, but owing to its small size has usually escaped obser- 

 vation. It has been reported from Macoupin county, Illinois, 

 and from Polk county, Iowa. 



Pleurotomaria speciosa MEEK & WORTHKN. 

 Pleurotomaria speciosa Meek & Worthen, 1860: Proc. Acad. Nat Sci., 



Phila., p. 459. 

 Pleurotomaria speciosa Meek & Worthen, 1866: Geol. Sur. Illinois, vol. II, 



p. 352, pi. xxviii, figs. 5i-c. 



Shell rather below medium size, conical, about as long as 

 broad. Whorls about seven in number, the last as long as 

 the spire, obliquely flattened above and angular toward the 

 top ; periphery sharp, convex below, with a very obtuse angu- 

 larity passing around the middle ; suture deep. Aperture sub- 

 quadrate. Surface marked by filiform revolving lines, about 



