PLATE XVII. 



From the Chalk Marl. 



PsEUDODiADEMA VARiOLARE, Bronyiiiart, sp. 



Fig. 1 a. Test, the natural size, with spines. British Museum. (P. 107.) 



1 h. Spine, greatly magnified. 

 Fig. 2. Test, magnified one half. In the cabinet of Dr. Wright, F.R.S.E. 

 Fig. 3 a. Lateral view, magnified one half. Do. 



3 b. Base view, do. Do. 



3 c. Upper surface, do. Do. 



Fig. 4. Ambulacral area, and zones and inter- ambulacral plates, magnified six times. 

 Dr. Wright's cabinet. 



Fig. 5 a. Upper portion of the ambulacra and poriferous zone, showing the bigeminal 

 pores, magnified six times. 

 5 h. Infra-marginal portion of the ambulacral area, showing the triple obfique pairs 

 of holes at the base of the area, magnified six times. 



