PLATE 51. 

 Melonechinus dispar (Fischer von Waldheim). Page 365. 



Figs. 1-3. Lower Carboniferous Limestone, Ratofka, Moscow, Russia, after Fischer von Wuldheim, 1848, Plate 3, figs. 



4a-4d. Holotype. 



Fig. 1. Probably magnified X 2. Six columns of plates in the ambulacral areas and four columns of plates in the inter- 

 ambulacrum; structurally the simplest species known in the genus. 



Fig. 2. Ambulacral plates enlarged; they are more hexagonal than in any specimens of other species seen. 

 Fig. 3. Single interambulacral plate with tubercles. Enlarged. 



Melonechinus parvus (Hambach). Page 365. 



Fig. 4. Lower St. Louis Limestone, Lower Carboniferous, St. Louis, Missouri. V. Springer Col!., 8,118, holotype (from 

 G. Hambach Coll.). Natural size. Ventral view, melon-like ribs are weakly marked; six columns of plates in 

 each ambulacral area at the mid-zone and six columns of plates in interambulacrum A at a point a little dorsal to 

 the mid-zone. Drawing, Plate 52, fig. 1. 



Melonechinus springeri sp. nov. Page 366. 



Fig. 5. St. Louis Group, Lower Carboniferous, Elizabethtown, Kentucky. F. Springer Coll., 8,103, holotype. Natural 

 size. A small species, with melon-like ribs strongly marked, six columns of plates in an ambulacral area at the mid- 

 zone. In interambulacra E, G, and I there are six columns of plates, but in interambulacra A and C a seventh column 

 is represented by a few plates dorsally. The apical disc measures proportionately about 23 % of the diameter of the 

 test, which is relatively large for the genus and family (p. 367). Drawings, Plate 52, figs. 2-6. 



Melonechinus crassus (Hambach). Page 367. 



Fig. 6. Lower St. Louis Limestone, Lower Carboniferous, St. Louis, Missouri. F. Springer Coll., 8,116, holotype (from 

 G. Hambach Coll., the original of Miss Klein's, 1904, Plate 1, figs. 2a-2d). Natural size. A massive species, with 

 strong rounded melon-like ribs. There are eight columns of ambulacral plates at the mid-zone and six columns of 

 interambulacral plates in areas A, C, E, and G, but area I is imperfect dorsally so that the number of columns is 

 uncertain. In the figure, the oral area is below. Hambach's published figure of this specimen is inverted. Draw- 

 ings, Plate 52, figs. 7-11. 



Melonechinus indianensis (Miller and Gurley). Page 369. 



Fig. 7. St. Louis Group, Lower Carboniferous, Greenville, Harrison County, Indiana. Univ. of Chicago Coll., 6,622, holo- 

 type. Natural size. Melon-like ribs strongly marked, a large, old-age individual. Eight columns of plates in an 

 ambulacral area at the mid-zone. In interambulacra A to G there are six columns of plates, but in I there are seven 

 columns and two plates representing an eighth column. The apical disc measures proportionately 16 % of the diam- 

 eter of the test (p. 370). Oculars are all insert, genitals are wide and high. Drawings, Plate 53, figs. 1-4. 



Fig. 8. St. Louis Group, Lower Carboniferous, Greenville, Harrison County, Indiana. F. Braun Coll. Natural size. 

 There are six columns of plates in each interambulacral area. The apical disc measures proportionately 18 % of the 

 diameter of the test. 



Fig. 9. Lower Carboniferous, Allen County, Kentucky. Mus. Comp. Zool. Coll., 3,147. Natural size. Eight columns 

 of plates in each ambulacral area, and six columns of plates in each interambulacral area. The sutures of the 

 plates are a good deal obscured by silicifi cation. 



Melonechinus septenarius Jackson. Page 373. 



Fig. 10. Warsaw Group, Lower Carboniferous, Buzzard's Roost, Franklin County, Alabama. Amer. Mus. Nat. Hist., 

 ^p, holotype. Natural size. The specimen is a siliceous internal mold, therefore the surface character js un- 

 known; eight columns of plates in the ambulacral area at the mid-zone and seven columns of plates in the inter- 

 ambulacral area. Drawing, Plate 53, fig. 5. 



Fig. 10 from photograph taken in New York; all others by F. A. Saunderson. 



