PLATE 48. 

 Oligoporus blairi Miller and Gurley. Page 351. 



Fig. 1. Keokuk Group, Lower Carboniferous, Boonville, Missouri. Univ. of Chicago Coll., 6,190 (the holotype of Oligo- 

 porus brllnlits Miller and Gurley, here considered a synonym of blairi). Natural size. Ambulacral plates at the raid- 

 zone are demi- and occluded, with scattered isolated plates. In interambulacrum A there are only four columns of 

 plates, an extreme radial arrested variation; interambulacrum C is only preserved dorsally, but at that zone there 

 are seven columns of plates in this area. Some tubercles and spines are in place on ambulacral and interambula- 

 cral areas. Drawing, Plate 47, fig. 6. 



Oligoporus coreyi Meek and Worthen. Page 353. 



Fig. 2. Keokuk Group, Lower Carboniferous, Crawfordsville, Indiana. Univ. of Michigan Coll., 147, holotype. Natural 

 size. Dorsal view; the specimen is silicified, and the surface is worn, so that details are clear only in parts. Ambul- 

 acra with demi-, occluded, and scattered isolated plates. In interambulacra A, E, and G, there are seven columns 

 of plates, but in C there are only six columns. In area I only six columns are visible but the area is imperfect 

 dorsally. Drawings, Plate 47, figs. 8, 9. 



Oligoporus sulcatus Miller and Gurley. Page. 354. 



Fig. 3. St. Louis Group, Lower Carboniferous, Hardin County, Kentucky, Univ. of Chicago Coll., 6,623, holotype. 



Natural size. Silicified specimen, ventral view. 

 Fig. 4. Same specimen, dorsal view. Natural size. Melon-like ribs are strongly marked. Ambulacra with demi-, 



occluded, and scattered isolated plates. All interambulacra with six columns of plates at the mid-zone, but with a 



seventh arising just above that zone in each area. Drawing, Plate 47, fig. 10. 



Oligoporus halli sp. now Page 355. 



Fig. 5. Keokuk Group, Lower Carboniferous, Boonville, Missouri. F. Springer Coll., 8,114, holotype (from G. Hambach 

 Coll., the original of Miss Klem's 1904, Plate 1, figs. 3a, 3b). Natural size. Melon-like ribs moderately developed. 

 Ambulacra with demi-, occluded, and scattered isolated plates. Interambulacra A, C, and I each have eight columns 

 of piates, but E and G have only seven. Drawings, Plate 47, figs. 11, 12. 



