EXem — Revision of the Palaeozoic Palaeechinoidea. 49 



1891, ArcJiaeocidaris edgarensis. Keyes, Proc. Acad. Nat. 

 Sci. Phil., p. 245. 



Primary spines long, cylindrical, tapering gradually. 

 Strongly striated ring at the base. Upper portion of the 

 spines for about three-fourths of their length are set with 

 short lateral spinules pointing upward. Spine terminates in 

 a mucronate point. 



Geological formation and locality: Upper Coal Measures, 

 near Baldwinsville, Edgar Co., 111.; Lower Coal Measures, 

 Des Moines, Iowa. 



7. Archaeocidaris gracilis Newberry. 



1861. ArcJiaeocidaris gracilis. Newberry, Ives' Colo. Expl. 



Exped., pt. 3, p. 117, pi. 1, figs. 4, 4 a. 

 1874. Archaeocidaris gracilis. Loven, Kongl. Svens. Vet- 

 ens. Akad. Handl., bd. 11, No. 7, p. 44. 

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

 p. 225. 

 Circle of small tubercles around the primary tubercle, which 

 is deeply perforated. Spines slender, conical, circular in sec- 

 tion, set with fine granulations, scattered toward the apex. 

 Basal ring crenulated and prominent. 



Geological formation and locality: Upper Carboniferous, 

 Banks of the Colorado Eiver. 



8. Archaeocidaris illinoisensis Worthen and Miller. 



1883. Archaeocidaris iUinoiensis. Worthen and Miller, 



Geol. Surv% 111., vol. 7, p. 338, pi. 31, figs. 1 a-b. 

 1889. Arcliaeocidaris illinoisensis. Miller, N. Amer. Geol. 



Pal., p. 225. 

 1895. ArcJiaeocidaris illinoisensis. Keyes, Proc. Iowa Acad. 

 Sci., vol. 2, p. 187. 

 Primary spines stout, cylindrical, tapering gradually. 

 Articulating ring subangular, just above which the spines are 

 slightly curved. Above this they are studded with short sharp 

 spinules directed outward and slightly upward. 



