PLATE 63. 



Lepidechinus irregularis (Keeping). Page 396. 



Figs. 1, 2. Lower Carboniferous Limestone, Hook Head, County Wexford, Ireland (after Keeping, 1876, Plate 3, figs. 6 

 and 7). Holotype in Sedgwick Museum, Cambridge, England, no. 12. 



Fig. 1. A small species with four or five columns of moderately imbricate pates in an interambulacral area; ambulacra 

 narrow. X 0.9. 



Fig. 2. Enlargement of an ambulacrum and interambulacrum. Ambulacra! plates are low and narrow; pore-pairs uni- 

 serial; interambulacrum with four columns and a trace of a fifth column as represented by one plate dorsally; plates 

 arc rounded hexagonal, imbricating moderately dorsally and from the center laterally. 



Lepidechinus iowensis sp. nov. Pago :'>'.>7. 



Fig. 3. Same specimen as photograph, Plate 62, fig. 1. Holotype. X 1.8. Ambulacral plates are low and narrow, with 

 two columns in each area ; pore-pairs uniserial. Interambulacra in each area with five columns of rounded hexagonal 

 plates imbricating moderately dorsally and from the center laterally and over the ambulacra. Tubercles are all 

 secondaries, uniform in size. A dorsal view of a lantern in place shows pyramids, braces, and teeth, which last are 

 MI mit^ly inclined, indicating a flaring lantern as in Archaeocidaris. 



Fig. 4. The same. X 3.5. Section looking ventrally to show the beveling of ambulacral and interambulacral plates, the 

 latter shaded for contrast. 



Lepidechinus tessellatus sp. nov. Page 397. 



Fig. 5. Same specimen as photograph, Plate 62, fig. 2. Holotype. X 1.8. Two columns of low plates in each ambulacral 

 area, imbricating moderately ventrally; six columns of rounded hexagonal median or pentagonal adradial plates 

 in each interambulacral area. Interambulacral plates imbricating moderately dorsally and from the center laterally 

 and over the ambulacrals. 



Fig. 6. Same specimen. X 3.4. Ambulacral detail enlarged, from the area marked X in fig. 5. 



Fig. 7. Same specimen as photograph, Plate 62, fig. 3. Paratype. X 1.7. Seen from the interior. The ambulacra are 

 wider than on the exterior. Six columns of plates in each interambulacral area and the plates are more sharply 

 hexagonal than on the exterior. Oculars each have one pore, and are exsert, an unusual Palaeozoic character (pp. 89, 

 221); each ocular plate adorally covers an ambulacrum and laterally in part an interambulacrum on either side 

 (p. 52). Each genital plate has a single pore in the middle of the plate, a feature which I have seen in no other 

 Palaeozoic type (pp. 171, 221). 



Fig. 8. Same specimen. Ocular and genital plates more enlarged. X 7. 



Fig. 9. Same specimen as photograph, Plate 62, fig. 4. Paratype. X 1.8. Six columns of moderately imbricating 

 plates in interambulacrum A; tubercles shown in one plate of area C. 



Fig. 10. The same specimen, enlarged to show an interambulacral plate beveling over an ambulacral on the adradial suture. 

 The interambulacral plate shaded. 



Fig. 11. The same specimen to show the imbricate edges of an interambulacral plate. 



Figs. 1 and 2 copied by W. M. Barrows, all others drawn by J. Henry Blake. 



