﻿PLATE LXI. 



Concavum-zone. 



Figs. 1, 2. — Sonnint a irregularis, 8. Buckman. 



Fig. 1. — Side view of an adult specimen showing persistence of spines to a late 

 date, followed by nearly upright ribs. The last half-whorl is body-chamber. 

 Bradford Abbas, Dorset. From my father's Collection. (Page 320.) 



(The plate is a copy of a photograph, and is within a fraction of natural 

 size, namely, 246 mm. (9y^ inches), as against 266 mm. (10^ inches), the diameter 

 of the fossil.) 



Fig. 2. — Outline of the aperture. Natural size. 



