PLATE 52. 



Melonechinus parvus (Hambach). 



Page 365. 



Fig. 1. Same specimen as photograph, Plate 51, fig. 4. Holotype. X 1.8. Six irregular columns of ambulacral plates 

 at the mid-zone. In area B as far adorally as it is preserved there are two columns of plates, deini- and occluded 

 in the right half-area, higher up dissociated isolated plates appear, higher again the isolated plates become more 

 frequent and make a continuous column, thus forming with the demi- and occluded plates three columns in a half- 

 area, the species character. In interambulacrum A (restored ventrally, as indicated by dotted lines) there are five 

 columns of plates at the mid-zone. A sixth column appears dorsally represented by one pentagonal plate with a 

 heptagon, H, on its left ventral border. In area C a peculiar pentagonal plate, X, appears in column 4, and the 

 adradial plate on its right has six instead of five sides as is usual in the plates of an adradial column. 



Melonechinus springer! sp. nov. 

 Figs. 2-6. Same specimen as photograph, Plate 51, fig. 5. Holotype. 



Page 366. 



Fig. 2. Upper part of the test. X 3.6. In the half-ambulacra there are three irregular columns of plates at the mid-zone, 

 higher up two columns with dissociated isolated plates, then two columns only and near the ocular one column 

 only in a half-area. Interambulacrum with six columns of plates at the mid-zone, a seventh appearing dorsally in 

 this area and also in area C. (Compare fig. 2 with text-fig. 19, p. 59; and figs. 2 and 3 with text-fig. 237, p. 231.) 



Fig. 3. Half-ambulacrum ventrally. X 3.6. Two columns of demi- and occluded plates ventrally, higher up an isolated 

 plate appears, then more isolated plates appear making three columns in the half-area. 



Fig. 4. Interambulacrum I, restored ventrally, as indicated by dotted lines, showing the introduction of columns 5 and 6. 

 X 1.8. 



Fig. 5. Ambulacral plates, sBowing tubercles and pore-pairs in peripodia. X 7. 



Fig. 6. Interambulacral plate with tubercles. X 7. 



Melonechinus crassus (Hambach). 



Page 367. 



Figs. 7-11. Same specimen as photograph, Plate 51, fig. 6. Holotype. 



Fig. 7. Interambulacrum C with a half-ambulacrum at the mid-zone. X 1.3. Column 1 is partially restored, as indicated 



by dotted lines. Columns 5 and 6 originate early; ambulacrum with four columns of plates in the half-area at the 



mid-zone. 

 Fig. 8. Ventral part of interambulacrum E. X 1.3. The basicoronal row is restored, as indicated by dotted lines; there 



are three plates in the second row, and four in the third, the fifth column appearing in the seventh row. 

 Fig. 9. Base of ambulacrum F. X 3.5. Ventrally, there are demi- and occluded plates only, higher up isolated plates 



appear in the middle line of the half-area. Compare the ventral plates of ambulacrum B in fig. 7. 

 Fig. 10. Spines in ambulacrum B. X 7.2. 

 Fig. 11. Spines in interambulacrum C, from area marked X in fig. 7. X 7.1. 



