SONNINIA DECORA. 361 
Sonninta susppEcorATA, S. Buckman. Plate LXXXIV, figs. 9—11. 
Discoidal, compressed, hollow-carinate. Whorls ornamented in the brephic 
stage with regular spines, in the neanic stage with coste, and at intervals spines ; 
in the ephebic stage with small, closely-set, direct, nearly upright, ventrally- 
inclined costs, occasionally connate on the inner third of the whorl. Ventral 
area subacutely arched, divided by a small, well-defined hollow carina. Inner 
margin ill-defined, subconvex. Inclusion about two-fifths. Umbilicus shallow. 
Whorl-section subelliptical. Suture-line with long, narrow-stemmed, ornate lobes 
—the superior lateral asymmetrical. 
The suture-line of this species shows that it has no connection with the 
submarginata-group—the narrow-stemmed and somewhat elaborate lobes indicate 
considerable anatomical differences ; and, in fact, like the last, it is differently 
ornamented and thinner. 
From decorata this species differs by the much smaller size of its more 
closely-set ribs, by the ribs being occasionally connate on the inner third instead of 
bifurcate towards the outer third of the whorl, by its thinner shape, and by the 
absence of nodicoste. It is presumably the descendant of decorata, showing 
further retrogression. 
Sonn. subdecorata is not a common species, though several specimens have been 
obtained at Bradford Abbas, Dorset, in the Concavum-zone. In figs. 9, 10, of 
Pl. LXXXIV are shown the side and front views of a specimen with well-preserved 
test ; the suture-line, fig. 11, is from another specimen. 
SONNINIA DECORA, S. Buckman. Plate LXXXIV, figs. 12—14. 
Discoidal, compressed, hollow-carinate. Whorls ornamented with numerous, 
small, direct, slightly-reclining, ventrally-inclined ribs,’ occasionally obscurely 
connate on the edge of the inner margin. Ventral area not defined, arched, 
divided by a small, well-defined hollow carina. Inner margin scarcely defined, 
steep. Inclusion about three-eighths. Umbilicus with a very slight excentric 
appearance. Aperture elliptical. Suture-line somewhat ornate. 
This species is, when adolescent, so exactly the morphological representation 
of adult subdecorata, that I have little hesitation in placing it in this connection. 
1 The details of just the centre have been obscured by the tool in cleaning, but some nodicoste 
may be detected in youth. 
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