﻿PLATE LVIII. 



Concavum-zone. 



SoNNINIA ACANTHODES, 8. Btickmail. 



Side view of an adult specimen showing the persistence of the spines to the 

 beginning of the last half-whorl, and the large reclining ribs 1 which follow. 

 Bradford Abbas, Dorset. From the Collection of Mr. Darrell Stephens, F.G.S. ; 

 now in my cabinet. The specimen is drawn the natural size. (Page 319.) 



1 No doubt some of these ribs would be spinous if the test were present. 



