50 Trans. Acad. Sci. of St. Louis. 



Geologiccal formation and locality: St. Louis Limestone, 

 Hardin Co., 111. 



9. Archaeocidaris keokuk Hall. 



1858. Archaeocidaris keokuk. Hall, Geol. Iowa, vol. 1, pt. 



2, p. 699, pi. 26, figs. 2 a, b. 

 1874. Archaeocidaris Keokuk. Love'n, Kongl. Svens. Vetens. 



Akad. Handl., Bd. 11, No. 7, p. 43. 



1889. Archaeocidaris keokuk. Miller, N. Amer. Geol. Pal., 

 p. 225. 



1894. Archaeocidaris keokuk. Keyes, Mo. Geol. Surv., vol. 

 4, p. 128. 



1895. Archaeocidaris keokuk. Keyes, Proc. Iowa Acad. Sci., 

 vol. 2, p. 186. 



Central tubercle papillif orm with a depressed space between 

 it and the annulation. Beyond the annulation is a flattened 

 elevation. Surface between this and the nodulose rim concave. 



Primary spines round, muricate, ridged and having spini- 

 form tubercles. Spines expand near the base into a subangu- 

 lar annulation. 



Geological formation and locality: Keokuk Limestone, 

 Warsaw, 111.; Clark Co. and Boonville, Mo. 



10. Archaeocidaris legrandensis Miller and Gurley. 



1890. Archaeocidaris legrandf^nsis . Miller and Gurley, 16th 

 Rep. Geol. Surv. Ind., p. 373, pi. 10, fig. 15. 



1895. Archaeocidaris legrandensis. Keyes, Proc. Iowa Acad. 

 Sci., vol. 2, p. 185. ^ 



Primary tubercles large, occupying about half the plate. 

 Annular ring obscure, with a concave depression around it 

 and a distinct elevation toward the margin. Margin studded 

 with obscure nodes. 



Primary spines very long, cylindrical and smooth. At the 

 base the spine is contracted a little with a slight swelling 

 immediately above. Spines taper gradually. 



Geological formation and locality : Kinderhook Group, Le 

 Grand, Iowa. 



