ARCHAEOCIDAHIS. !>.-,. t 



Spines with four vertical rows of spinuli-: 

 A. rankini Young (Europe), p. 276. 



Spines with six vertical rows of spinules: 

 A. prisca (Minister) (Europe), p. 276. 



Spines with many vertical ridges, which bear spinulcs directed diwtally: 

 .1. trrnckn Tornquist (Europe), p. 276. A. halliana (Geinitz) (Europe), p. 279. 



A. urii (Fleming) (Europe), p. 276. .1. muensleriana (Koninck) ( Knn M ,,->, p. 280. 



Spines inflated, club-shaped: 



A. forbesiana (Koninck) (India), p. 280. .1. ./,. /,. Girty (America), p. 281. 



A. spinoclavata Worthen and Miller (America), A. ctavata (Eichwald) (Europe), p. 2M.'. 



p. 281. 



"Archaeocidaris wortheni Hall. 

 Text-figs. 26, p. 70; 47, p. 80; Plate 8, figs. 5, 6; Plate 9, figs. 6-11. 



Archacocidaris wortheni Hall, 1858, p. 700, Plate 26, figs. 4a^tg; Love"n, 1874, p. 43; Quenstedt, 1875, 

 p. 372, Plate 75, figs. 10-14; Zittel, 1879, p. 485, figs. 343a-343c (not 343d, which in tln\ ami -th.-r 

 editions is evidently Archcwocidaris kcokuk Hall); (?) Walcott, 1884, p. 212; Keyes, 1894, p. 128, 

 Plate 17, figs. 3a, 3b; 1895, p. 187, Plate 20, figs. 3a, 3b; Jackson, 1896, p. 214, Plate 8, figs. 43-16; 

 Tornquist, 1897, p. 770, Plate 21, fig. 5; Klem, 1904, p. 61. 



Cidarotropus wortheni Pomel, 1883, p. 113; Lambert and ThieYy, 1910, p. 125. 



Test spheroidal, but flattened mechanically in the known specimens. The ambulacra 

 are narrow, sinuous, conforming to the outline of the adambulacral plates. Ambulacral plates 

 are low, imbricating moderately adorally, beveled under the adradials, with pore-pairs uni- 

 serial. Interambulacra are broad, with four columns of plates in each area, imbricating mod- 

 erately aborally and from center laterally and over the ambulacrals. There are four plates 

 in the basicoronal row of each interambulacral area, indicating an extensive resorption of the 

 corona in the advance of the peristome (p. 73). Interambulacral plates hexagonal, except the 

 adradials, somewhat wider than high, with a wide scrobicular area as seen well in Plate 8, 

 fig. 5, and Plate 9, fig. 9. Secondary tubercles are limited to a narrow border parallel to the 

 edges of each plate. The primary spines are long, slender, slightly arcuate, from the milled 

 ring tapering to the distal end. Small secondary spines are associated with the secondary 

 tubercles. The peristome has ambulacral plates radially and numerous scale-like non-ambula- 

 cral plates interradially situated, all imbricating adorally. The dorsal area is known only 

 partially (Plate 8, fig. 6). The lantern is of the typical character of the genus (Plate 9, fig. 10). 



St. Louis Limestone, Lower Carboniferous, St. Louis, Missouri. The cotypes and several 

 other specimens including one fine slab with ten tests are in the American Museum of Natural 



