PLATE 8. 

 Bothriocidaris pahleni Schmidt. Page 242. 



Fig. 1. Diluvial-Geschichte, Ordovician, Rostov, Russia. Height 16.2 mm., diam. 16 mm., from a plaster cast, Mus. 

 Comp. Zool. Coll 3,082 (from R. T. J. Coll.). Original at Rostov. X 2. Two columns of high hexagonal plates 

 in each ambulacral area and one column of plates in each interambulacral area, the latter darkened for contrast. 

 (Compare drawing of another specimen, Plate 1, fig. 3.) 



Arbacia punctulata (Lamarck). Page 39. 



Fig. 2. Woods Hole, Massachusetts. Almost completely tetramerous, but there are five genital plates. The wanting 

 parts are a tooth and ocular II, with its associated parts, which are ambulacrum II, the left half of interambula- 

 crum 2, and the right half of interambulacrum 1. Same specimen as Plate 6, fig. 1. 



Strongylocentrotus drobachiensis (O. F. Muller). Page 47. 



Fig. 3. Dumpling Islands, North Haven, Maine. R. T. J. Coll., 838. Natural size. Completely hexamerous; structure 

 exactly as in Plate 7, fig. 7. This specimen is oriented and the additional area calculated from the oculars I, V 

 insert, the position of the madreporite and the fused genitals. 



Echinarachnius parma (Lamarck). Page 49. 



Fig. 4. Partially hexamerous. Natural size. Pentamerous ventrally, but a sixth ambulacrum and interambulacrum are 

 added dorsally. Same specimen as Plate 7, fig. 9. 



Archaeocidaris wortheni Hall. Page 259. 



Fig. 5. St. Louis Group, Lower Carboniferous, St. Louis, Missouri, Amer. Mus. Nat. Hist. ' \ 47 , cotype. Natural size. 

 Ventral view, showing narrow ambulacral areas and four columns of plates in each interambulacrum. The basal 

 terrace is clear on interambulacral plates. The peristome and lantern are in part preserved orally. This is one 

 of the two most nearly complete specimens known in the genus. Drawings, Plate 9, figs. 6-8. 



Fig. 6. Same specimen. Dorsal view. Primary spines and lantern in place. 



Archaeocidaris legrandensis Miller and Gurley. Page 260. 



Fig. 7. Keokuk Group, Lower Carboniferous, Boonville, Missouri. Univ. of Chicago Coll., 8,855. X 1.5. There arc 



four columns of plates in each interambulacrum. Drawing, Plate 9, fig. 12. 

 Fig. 8. Same locality. Museum and Cat. no. as fig. 7. X 1.5. With primary and secondary spines in place. Drawing, 



Plate 9, fig. 13. These two specimens are the cotypes of Eocidaris blairi Miller, here considered a synonym. 



Archaeocidaris newberryi Hambach. Page 269. 



Fig. 9. St. Louis Group, Lower Carboniferous, St. Louis, Missouri. F. Springer Coll. 8,119 (from G. Hambach Coll.), 

 holotype. Natural size. Drawing, Plate 13, figs. 15a, 15b. 



Archaeocidaris triserialis (M'Coy). Page 275. 



Fig. 10. Arenaceous Limestone, Lower Carboniferous, Killycloghy, Lisbellow, County Tyrone, Ireland. Griffith Coll., 

 Science and Arts Museum Coll., Dublin, holotype. Natural size. The specimen consists of spines only. 



Figs. 1, 2, 4-9 photographed by F. A. Saunderson; fig. 3 photographed by H. W. Tupper; fig. 10 photographed in 

 Dublin by A. C. Bridle. 



