PLATE XXVII. 



From the Upper White Chalk. 



Fig. 1 a. Cyphosoma Wetherelli, Forbes. Test, natural size. Museum of the Royal 



School of Mines. (P. 139.) 



1 b. „ „ The upper surface of do., uiagnitied twice. 



1 c. „ „ The under surface of do., do. 



1 d. „ „ The lateral view of do., do. 



1 e. „ „ Areal plates and zones, magnified six times. 



1 /. ,, „ Lateral view of a single tubercle, mag- 



nified. 



1 y. „ „ Upper portion of an ambulacrum, magnified 



six times. 



1 h. „ „ Inferior portion of do., do. 



