CHAPTER XIII. 



GASTEROPODS. 



Dentalium primarium HALL. 



Dentali urn primarium Hall. 1858: Geology Iowa, vol. I, p. 666, pi. xxxiii, 

 fig. 16. 



Shell large, stout, nearly straight ; surface smooth. 

 Horizon and localities Lower Carboniferous, Keokuk 

 limestone : Warsaw ( Illinois ). 



Dentalium missouriense SWALLOW. 



Dentalium mis&ouriense Swallow, 1863 : Trans. St. Louis Acad. Sci., vol. 

 II, p. 99. 



Shell rather large, thin, slightly curved, and marked with 

 small longitudinal ribs. 



Horizon and localities. Lower Carboniferous, Kaskaskia 

 limestone : Ste. Mary ( Ste. Genevieve county ). 



Dentalium meekianum GEINITZ 



Dentalium meekianum Geinitz, 1866 : Garb, und Dyas la Nebraska, p. 13, t. 



i, fig. 20. 

 Dentalium meekianum Meek & Worthen, 1873: Geol. Sur. Illinois, vol. V, 



p. 590, pi. xxix, figs. 8a-c. 



Dentalium meekianum Keyes, 1SSS: Proc. Acad. Nat. Sci., Phila., p. 234. 

 Dentalium meekianum Keyes, 1891: Proc. Acad. Nat. Sci., Phil*., p. 251. 



Shell rather small, curved, subcylindrical, ornamented by 

 numerous fine oblique lines. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



In the Carboniferous rocks of the Mississippi basin, four 

 distinct types of Dentalium are recognized. The first has the 

 surface ornamentation composed of a series of ridges trans- 



