PLATE XCIX. 



Concavum-zone. 

 Figs. 1 — 3. — Sonninia duplicata, 8. Buchnan. 



Fig. 1. — Side view, showing regular central spines, later irregularly-placed 

 spines, later ribs somewhat in pairs. Bradford Abbas, railway cutting. My 

 Collection. (Page 402.) 



Fig. 2. — Outline of the whorl-section. 



Fig. 3. — Suture-line showing tetradactyloid L, the outer lobule deeply cleft, the 

 terminal lobule isosceloid. 



Figs. 4 — 6. — Sonninia camura, 8. Buchnan. 



Fig. 4. — Side view, showing the large ribs of maturity and the peculiar 

 curvature of the umbilicus. (The last quarter-whorl is set a little more angularly 

 than the drawing suggests — it has somewhat of a "scaphitoid" bend.) This 

 drawing is a copy from a photograph, and is much reduced, to about three-tenths 

 of natural size, being 68 mm. in diameter as against 228 mm., the size of the 

 specimen. Bradford Abbas. My Collection. (Page 403.) 



Fig. 5. — Outline of the whorl-section. Natural size. 



Fig. 6. — Portions of two suture-lines taken from another specimen, showing a 

 superior lateral lobe with a duplicated outer lobule, thus making the lobe 

 tetradactyloid. 



