PLATE VI. 



Sowerbyi-zone. 



Lioceras concavum (Sowerby). Var. A. 



Fig. 1. — Large adult specimen, showing the greater portion of the termination 

 of the body-chamber, also the peculiar increase in the width of the umbilicus, due 

 to the recession of the inner margin of the body-chamber from the regular line of 

 coil round the centre. The umbilicus (which is not quite distinctly shown in the 

 figure) is, until about the last whorl, regularly hollow like the inside of a thimble- 

 top, the inner whorls not projecting at all. The inner area of the whorl is also 

 shown somewhat too flat, and the outer area is too steep. Side view. Natural 

 size. My Collection. Bradford Abbas, Dorset. 



Fig. 2. — Front view of same, showing the small amount of keel possessed in 

 adult age. The inclusion is rather more than is shown. 



