PLATE 55. 

 Melonechinus multiporus (Norwood and Owen). Page 375. 



Figs. 1-3. St. Louis Group, Lower Carboniferous, St. Louis, Missouri. 



Fig. 1. F. Springer Coll., 8,106 (from G. Hambach Coll., K 6, the original specimen of Miss Klem's, 1904, Plate 3, figs. 

 6a-6e). Enlarged X 1.2. Diameter through the plane J, E, 63 mm., height 57 mm. Ventral view, a small but 

 marvellously perfect specimen. Melon-like ribs low, rounded. In four ambulacral areas the plates ventrally are 

 in four columns there being two columns of demi-plates and two columns of occluded plates in each area as usual 

 at this zone in the species and the genus, the number of columns in each area increasing in passing dorsally. As an 

 exception in area B ventrally there are two primary plates representing two columns in this zone as a unique regres- 

 sive radial variation. In interambulacrum G there are two plates in the basicoronal row, three plates in the second 

 row, and four plates in the third row. The fifth column originates in the sixth row with a heptagon on the left 

 border of the initial pentagon. The sixth column originates in the tenth row with a heptagon on the right of its 

 initial pentagonal plate (compare Plate 57, fig. 1, and text-fig. 245, p. 382). The other interambulacral areas are 

 similar except that the two plates of the basicoronal row are not complete in each area. 



Fig. 2. The same specimen, dorsal view. Enlarged X 1.2. Eight columns of plates in each interambulacral area, and 

 these plates dorsally approach a rhombic form. Insert ocular and genitals are all in place. The apical disc measures 

 proportionately about 15% of the diameter of the test. Drawings of this exceptionally fine specimen, Plate 57, figs. 

 1-3; text-figs. 245, 246, p. 382. (See pp. 230, 376, 379, 381-384.) 



Fig. 3. F. Springer Coll., 8,109 (from G. Hambach Coll., K 9, the original specimen of Miss Klein's, 1904, Plate 4, fig. 9d; 

 Plate 5, figs. 9a, 9b). Natural size. An exceptionally large specimen, the largest seen of this species. There are 

 nine columns of plates in interambulacral areas C, E, and G. Four oculars and all genitals are well preserved. 

 Oculars are insert and cover the ambulacra and laterally the interambulacra in part on either side, as seen in several 

 areas. Genital E has three, and G four pores; the other genitals have apparently three pores each, but the number 

 may be four in one or more of these plates as confusing accessory pits exist. The apical disc measures proportion- 

 ately about 15% of the diameter of the test (pp. 376, 377, 379). 



