PLATE 59. 

 Melonechinus keepingi sp. nov. Page 384. 



Figs. 1-3. Same specimen as photograph, Plate 5S, fig. 1. Holotype. 



Fig. 1. Upper part of a test. X 2.7. Ambulacrum with twelve columns of plates at the mid-zone; there are only two 

 plates in the area dorsally, increasing passing ventrally to the full number of twelve columns at the mid-zone. (Com- 

 pare text-fig. 237, p. 231.) Six columns of plates in the interambulacral area near the mid-zone, partly restored as 

 indicated by dotted lines. The adambulacral columns 1 and 2 drop out dorsally, above which 3 and 4 become the 

 adradial columns, a senescent character indicating an old-age individual. 



Fig. 2. Ambulacral plates, showing pore-pairs and tubercles. X 2.8. 



Fig. 3. Interambulacral plates, showing tubercles. X 2.7. 



Melonechinus giganteus (Jackson). Page 389. 



Fig. 4. Same specimen as photograph, Plate 58, fig. 2, (holotype of XI. granulatus Troost, here considered a synonym). 

 X 1.3. Twelve columns of plates in an ambulacral area and six of the columns of interambulacrum A are in place; 

 the rest are wanting on the right, but how many columns are absent is unknown (p. 392). 



Melonechinus etheridgii (Keeping). Page 385. 



Fig. 5. Same specimen as photograph, Plate 58, fig. 3. Paratype. X 0.9. There are six columns of plates in the left 

 half-ambulacrum, with also a few plates of the right half-ambulacrum. There are six columns of interambulacral 

 plates in place and a seventh or adambulacral column is restored on the left of the figure as indicated by dotted 

 lines (p. 387). 



Fig. 6. Same specimen as photograph, Plate 58, fig. 4. Holotype. X 1.4. Part of a half-ambulacrum. The plates of 

 the median occluded column b are only slightly wider than the plates of isolated columns (p. 386). 



Fig. 7. Lower Carboniferous Limestone, Frome, Somerset, England. British Mus. Coll., E 1,400. Ambulacral plates 

 with pore-pairs and tubercles (p. 388). X 2.7. 



Fig. 8. Lower Carboniferous, Coplaw, Clitheroe, Lancashire. Museum of Practical Geology Coll., 10,303. X 2.8. Am- 

 bulacral plates seen from the interior, face of plates rounded inwardly, pores about in the middle of the plates instead 

 of toward the next interambulacrum as on the exterior (p. 387). 



Figs. 9-11. Lower Carboniferous Limestone, Frome, Somerset. British Mus. Coll., E 1,400. X 2.7. 



Fig. 9. Interambulacral plate with tubercles and spines (p. 388). 



Fig. 10. Adradial plate with beveled adradial suture face (p. 388). 



Fig. 11. Adradial plate with facets for articulation with the ambulacral plates on the adradial face (p. 388). 



Melonechinus giganteus (Jackson). Page 389. 



Figs. 12-15. Same specimen as photograph, Plate 60, fig. 3. Holotype (after Jackson, 1S96, Plate 5, figs. 21-24). 



Fig. 12. Ambulacral detail from the right lower side of ambulacrum B (see photographic figure, Plate 60, fig. 3). X 2. 

 Only five columns of plates in a half-area are seen in this figure whereas six occur in a half-area at the ambitus, as 

 seen in Plate 61, fig. 8. (Compare figs. 12 and 13 with text-fig. 237, p. 231.) 



Fig. 13. Ventral portion of the test. X 2. Ambulacra have four columns of plates ventrally in each area; in the inter- 

 ambulacra the basicoronal row is wanting, but is restored in area A as indicated by dotted lines. There are three 

 plates in the second row, four plates in the third row, and five plates in the fifth row. 



Fig. 14. Interambulacrum A. Natural size. The basicoronal row is wanting. In the first row preserved there are three 

 plates, in the next row four plates; the columns 5, li, ami 7 originate very early, showing an accelerated development. 

 Column S originates early; column 9 originates with a tetragonal plate against which are two heptagons, H', H", 

 to compensate for the two sides wanting. Above the tetragon is one row of eight plates, then column 9 begins 

 again with a pentagonal plate, with a heptagon, H, on its right ventral border. This is a very exceptional anomaly 

 (compare Plate 50, figs. 2, 3). Column 10 originates just below the mid-zone, and column 11 in the dorsal third of 

 the area; column 11 drops out dorsally toward the apical disc, a senescent character (p. 391). 



Fig. 15. A single interambulacral plate with tubercles. X 4. 



Figs. 1-3, 5-11 drawn by A. T. Hollick; fig. 4 by J. Henry Blake; figs. 12-15 by J. H. Emerton. 



