﻿PLATE LXIX. 



Concavum-zone. 

 Figs. 1 — 3. — Sonninia dominans, S. Buckman. 



Fig. 1. — Side view of a form with rather small, regular, closely -set ribs. In 

 many respects this form is intermediate between marginafa (PI. LXII) and 

 dominans (PI. LXVI), and shows the development. Natural size. Bradford 

 Abbas, Dorset. My Collection. (Page 322.) 



Fig. 2. — Section of the whorl in outline. 1 



Fig. 3. — A part of the suture-line. 



1 The included whorl and the inner part of embracing whorl both rather too thin. 



