SONNINIA CRASSINUDA. 399 



Septation alone would group this species with Sonn. regularis or Sonn. crassa. 

 The strong costation which follows the spinous stage of that species, and the weak 

 costation which follows the same stage in this form, prevent its being considered 

 with them. It is this character of weak costation which connects this species 

 with the succeeding forms. 



Sonninia divbrsa, 8. Buchman. Plate CM, fig. 8. 



See Plate LXXXIII, figs. 1—4; Plate LXXXI, figs. 5—6, and 

 page 355. 



Add to description : — Suture-line of the type-form with fairly long lobes ; 

 L with intra-axial, anisosceloid terminal lobule and anisometric lateral lobules. 



Sonninia l^ivigata. Plate CI, figs. 7 — 9 (variety) ; Plate CIII, fig. 9. 

 See Plate LXXXII, figs. 5, 6, and page 356. 



Add to description : — Suture-line of type hardly to be followed with certainty ; 

 L with very anisosceloid terminal lobule, the lobe presumably degenerate. Suture- 

 line of variety : L with anisosceloid terminal lobule, anisometric lateral lobules, 

 outer distinctly tripartite. 



The form considered to be a variety is slightly more spinous in the umbilicus 

 than the type. If the suture-line shown by the type be considered to indicate 

 septal degeneration — and this may possibly have begun in this degenerate form 

 — then the suture-line of the variety may be thought to show the pattern of the 

 septa before degeneration commenced. In outline it agrees fairly — allowance being 

 made for difficulty in tracing the septa of the type. 



The variety came from Stoke Knap, near Broad Windsor, Dorset, doubtless 

 from the Concavum-zone. It was obtained by Mr. B. Wilson, F.G.S., who very 

 kindly allowed me to add it to my collection. 



Sonninia crassinuda, 8. Buckman. See Plate LXXXI, figs. 1 — 4, and page 351. 



The septa are unknown, but external characters (see page 348) seem to place 

 the species here in connection with Sonn. crassicostata. 



