SONNINIA CONTUSA. 409 



more umbilicate, more coarsely and distantly ribbed, and by having a more 

 brevilobate, much less ornate, suture-line. From Sonn. dominatrix (p. 392) 

 it is distinguished by being more spinous, more umbilicate, less costate, 

 and by its asymmetrical L. In shape, umbilication, and spinosity it resembles 

 Sonn. dominica (p. 410) ; but the irregularity of less prominent costee, the 

 greater thickness, and the more brevilobate suture-line lacking the subpendulous 

 outer lobule of L, are points of distinction for this species. 



Sonn. dominata occurs in the Concavmn-zone of Bradford Abbas. It is 

 illustrated in PI. XCVII : fig. 1, side view; fig. 2, outline of whorl-section, both 

 half natural size ; fig. 3, portions of two septa. 



Sonninia oontusa, S. Buchanan. Plate LXXXVIII, figs. 5 — 7. 



Discoidal, compressed, carinate. Whorls practically smooth in adult except for 

 some obscure irregularities. (Immature whorls with small, obscure, closely-set, 

 direct costae — details of centre not preserved.) Ventral area arched, divided by a 

 small, ill-defined, rounded, obsolescent carina. Inner margin fairly defined, 

 steeply sloped, flat. Inclusion about three-tenths. Umbilicus open. Suture- 

 line with asymmetrical L, the terminal lobule intra-axial, anisosceloid ; lateral 

 lobules degenerate, anisometric. 



The more concentric umbilicus separates this species from the other smooth, 

 or nearly smooth forms. It is much thicker than $. insequa (p. 400), with more 

 squared-up whorls ; it has a more concentric umbilicus, with deeper inner marginal 

 walls ; it is also smoother, and such costation as it possesses is more regularly 

 disposed. 



Sonn. contusa has a very degraded L, the lateral lobules being almost in a 

 vestigial condition, and the cruciform arrangement of L being almost lost. The 

 proportions suggest its association with S. dominata, and there is nothing in the 

 superior lateral lobe to negative this. 



This species occurs in the Concavum-zone at Bradford Abbas. It is illustrated 

 in PI. LXXXVIII: fig. 5, side view; fig. 6, outline front view, both one-half 

 reduced ; fig. 7, the superior lateral lobe. 



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