PLATE 13. 



Archaeocidaris agassizi Hall. Page 266. 



Figs. 1-4. Burlington Limestone. Lower Carboniferous, Burlington, Iowa. 



Fig. 1. After Hall, 1858, Plate 26, figs. Ib, Ic, Id. Cotypes. a, plate enlarged, basal terrace clear; b. the same in 



profile; c, spine, which is elliptical in cross section. X 1.8. 

 Fig. 2. Univ. of Michigan Coll., 1,580. X 3.8. Pyramid with tooth in place, the pyramid dorsally and the tooth ven- 



trally and dorsally are restored as indicated by dotted lines. 

 Fig. 3. F. Springer Coll., 8,100. X 1.8. Showing ambulacra, and four columns of interambulacral plates in area I; 



a few ambulacral plates are on the peristome. 



Fig. 4. F. Springer Coll., 8,087. X 3.7. Ambulacral plates with lateral bevel, interambulacral plates, pyramid with 

 epiphyses and brace. The perforated, elongate plates are unlike anything seen in other species; they may be genitals. 



Archaeocidaris illinoisensis Worthen and Miller. Page 266. 



Fig. 5. St. Louis Group, Lower Carboniferous, near Illinois Furnace, Hardin County, Illinois (after Worthen and Miller, 

 1883, Plate 31, fig. la, pars, fig. Ib). Cotypes. X 0.9. Spines swollen, with fine spinules. 



Archaeocidaris coloradensis nom. nov. Page 267. 



Fig. 6. Crinoidal Limestone, Upper Carboniferous, Northern Arizona. Columbia Univ. Coll., 6,900 G, cotype. X 0.9. 

 Fragment from shaft of a primary spine, muricate. 



Archaeocidaris keokuk Hall. Page 267. 



Fig. 7. Keokuk Group, Lower Carboniferous, Warsaw, Illinois, (after Hall, 1858, Plate 26, figs. 2a, 2b) cotypes. a. 

 plate enlarged, shows basal terrace; b, spine slightly enlarged, with numerous fine spinules. 



Archaeocidaris gracilis Newberry. Page 267. 



Fig. 8. Crinoidal Limestone, Upper Carboniferous, Canon, Diamond River (Colorado ?). Columbia Univ. Coll., 603 

 and 604, holotype. X 0.9. Spine slender, bears fine spinules. 



Archaeocidaris aculeata Shumard. Page 268. 



Fig. 9. Topeka Limestone, Carboniferous (Coal Measures), Topeka, Kansas. Indiana Univ. Geological Survey Coll. 

 X 1.9. a, b, dissociated plates; c-f, spines with small irregularly placed spinules. 



Archaeocidaris shumardana Hall. Page 268. 



Fig. 10. Warsaw Limestone, Lower Carboniferous, Warsaw, Illinois (after Hall, 1858, Plate 26, figs. 3b-3d). Cotypes, 

 a, plate enlarged; b, same in profile; c, spines with fine spinules. X 1.9. 



Archaeocidaris edgarensis Worthen and Miller. Page 269. 



Fig. 11. Upper Coal Measures, one mile east of Baldwinsville, Edgar County, Illinois (after Worthen and Miller, 1883, 

 Plate 30, figs. 15a-15c). Cotypes. a, single plate; b, spine; c, base of spine, enlarged. 



Fig. 12. Junietta Group, Carboniferous (Coal Measures), Manhattan, Kansas. J W. Beede Coll. X 2.8. A right 

 half-pyramid, face view, epiphysis wanting; p. s., pyramidal suture. 



Fig. 13. Same specimen, side view, with ridges for the attachment of interpyramidal muscle. X 2.8. 



Fig, 14. Same specimen, inner view, showing pyramidal suture and dental slide. X 2.8. 



Archaeocidaris newberryi Hambach. Page 269. 



Fig. 15. Lower St. Louis Limestone, Lower Carboniferous, St. Louis, Missouri. F. Springer Coll., 8,119 (from G. Ham- 

 bach Coll.), holotype. X 1.8. a, plates with primary and secondary spines in place; b, a nearly perfect primary 

 spine, spinules directed distally, in series. Same specimen as photograph, Plate 8, fig. 9. 



Archaeocidaris trudifer White. Page 269. 



Fig. 16. Red Wall Limestone, Carboniferous (Coal Measures), Camp Apache, Navajo County, Arizona (after White, 1877, 

 Plate 6, figs. 8a, 8b). " U. S. Nat Mus. Coll., 8,471, cotypes. X 0.9. a, hexagonal interambulacral plate; b, 

 primary spine, restored proximally and distally as indicated; spinules directed distally, irregularly distributed. 



Figs. 2-4, 8, 9, 12-15, drawn by J. Henry Blake; all others copied by W. M. Barrows. 



