PLATE XXI. 



From the Chloritic Marl. 



Fig. 1 a. P.SF,UDODiADEMA ORNATUM, Gold/uss. Upper surface, magnified one half, in the 

 cabinet of Dr. Wright, F.R.S.E. (P. 103.) 



1 b. Lateral view of the same test, magnified one half. 



1 c. Portion of the ambulacra, inter-ambulacra and pores, nuigiiified four times. 



1 d. Do. do. and spine, magnified four times. 



From ihe Grey Chalk. 



Pig. 2 a. Another specimen, with spines, in the cabinet of the Rev. T. Wiltshire, F.G.S. 



2 h. Portion of the ambulacra, inter-ambulacra and zones, magnified four times. 



Fig. ;3 a. PsEUDODiADEMA NoKMANivE, Cotteaii. Upper surface of the test, natural size, 

 in the cabinet of the Rev. T. Wiltshire, F.G.S. (P. 105.) 



3 b. Lateral view of the same, natural size. 



3 c. Ambulacral and inter-ambulacral plates, magnified four times. 

 3 (1. Ambulacral area, magnified three times. 



