PLATE XVII. 



From the Chalt Marl. 



PsECDODiADEJiA TARiOLAKE, BroHgiiiart, sp. 



Fig. 1 a. Test, the uatural size, with spines. British ^luseum. (P. 107.) 



1 b. Spine, greatly magnified. 

 Fig. il. 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 o. L pper portion of the ambulacra and poriferous zone, showing the bigeminal 

 pores, magnified six times. 



5 h. Infra-maiginal portion of the ambulaci-al area, showing the triple oblique pairs 

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



