PLATE XXVII. 



From the Upper White Chalk. 

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



School of Mines. (P. 189.) 



1 h. „ „ The upper surface of do., magnified twice. 



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



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



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



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



nified. 



I y. „ ^, Upper portion of an ambulacrum, magnified 



six times. 



1 h. „ Inferior portion of do., do. 



