Klem — Revision of the Palaeozoic Palae'echinoidea. 57 



20. Arciiaeocidaris spinoclavatus Worthen and Miller. 



1873. Archaeocidarifi? (sj). undet). Meek and Worthen, 



Geol. Surv. 111., vol. 5, pi. 24, figs. 13a-e. 

 1883. Arckaeocidaris spinoclavatus. Worthen and Miller, 



Geol. Surv. 111., vol. 7, p. 337, pi. 30, figs. 14a-e. 

 1889. Archaeocidaris spinoclavata. Miller, N. Amer. Geol. 



Pal., p. 225. 

 1895. Ai'chaeocidaris spinoclavatus. Keyes, Proc. Iowa 



Acad. Sci., vol. 2, p. 190. 

 Primary spines long, stout, cylindrical at the base, growing 

 larger gradually toward the apex and abruptly diminishing to 

 an obtuse clavate end. The upper end of the spine is thickly 

 covered with nodose spinules directed upward. On the 

 remaining part of the spine the spinules are smaller and 

 fewer in number. Basal ring smooth. 



Geological formation and locality: Coal Measures, St. 

 Clair and Marshall Cos., 111. 



21. Archaeocidaris triplex W^hite. 



1881. Archaeocidaris trijjlex. White, U. S. Geog. Geol. 



Surv. W. 100th Mer., vol. 3, Supp. Appendix, 



p. XXII., pi. 4, figs. 3 a-c. 

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



p. 225. 

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



vol. 2, p. 191. 

 1903. Archaeocidaris triplex? Girty, U. S. Geol. Surv., 



Professional Paper No. 16, p. 330. 

 Areolar surface plain or having only a single circle between 

 the primary tubercle and the outer border. Primary tubercle 

 small and surrounded by a prominent border. 



Primary spines large, strong, subtriangular and spinulose. 

 Spinules stout, short and prominent, rather far apart in three 

 rows from a short distance above the base. Basal ring prom- 

 inent and finely crenulated at the edge. 



