PLATE 66. 

 Perischocidaris harteiana (Baily). Page 408. 



Fig. 1. Lower Carboniferous, west shore of Lough Esk, about six miles from Donegal, Ireland. Trinity College Coll., 

 Dublin. Holotype. Natural size. The specimen is an external sandstone mold. Six columns of plates in each 

 ambulacral area at the mid-zone. Five columns of plates in each interambulacral area near the mid-zone, decreas- 

 ing in the number of columns dorsally. Genitals and oculars all in place. Drawings, Plate 67, figs. 1-3. On the 

 left in the figure is seen an impression of a second fragmentary specimen. 



Fig. 2. Plaster cast of same. Natural size. As this is a replica of the original specimen, the lettering is reversed from that 

 of the sandstone mold (fig. 1). 



Proterocidaris giganteus Koninck. Page 410. 



Fig. 3. Lower Carboniferous, Dinant, Belgium (after Fraipont, 1904, Plate 4, fig. 2, where it is called Oligoporus soreili 

 sp. nov., here considered a synonym). Natural size. This specimen represents a curious condition of preservation 

 in which most of the test is intact and viewed from the dorsal side, but one interambulacrum I and two adjacent half- 

 ambulacra H and J, are spread out (like peeling down a segment of an orange) and viewed from the interior. Four 

 columns of plates in an ambulacral area; a half-area with two columns of plates is seen from the interior in area J. 

 Eleven columns of interambulacral plates are seen at the mid-zone as viewed from the interior in interambulacrum 

 I ; but on the right-hand side of the area a twelfth column appears a little dorsal to the mid-zone. In area I, which 

 is seen from the interior, the plates imbricate adorally and toward the center, largely covering the central column. 

 In other areas seen from the exterior, the interambulacral plates imbricate aborally, and from the center laterally. 

 Plates with tubercles and spines. (In the figure the two letters A in white, are from Fraipont's original photograph 

 and signify ambulacral areas.) Drawings, Plate 67, figs. 6 and 7. 



Figs. 1 and 2 from photographs taken by A. C. Bridle in Dublin; fig. 3 copied by F. A. Saunderson. 



