406 INFERIOR OOLITE AMMONITES. 



to about 70 mm. diameter, with direct, undulate, reclined nodicostas, or sometimes 

 sub-bullicostse, obscure but inclined ventrally. Ventral area arched, medianly 

 flattened, divided by a fairly denned, small, rounded hollow carina. Inner margin 

 scarcely defined, convex. Inclusion one-third. Umbilicus spinous with rather 

 gibbous-sided whorls. Whorl-section gibbous-sided, quadrate-oblong. Suture-line 

 latilobate ; L nearly symmetrical, the terminal lobule slightly intra-axial, anisosce- 

 loid, inequicellate, the lateral lobules isometric. 



This species resembles Sonn. spinicostata ; and the likeness is exaggerated by 

 the reduction of the figure of that fossil, and by the features of delineation noticed 

 in the explanation of PI. LXXIII. It differs in the strength of its ornamentation, 

 the smaller size of the costse, and the knobs on the costge of the ultimate whorl 

 nearly obsolete at a diameter when those of spinicnstata are large and pronounced. 

 In fact, in ornamentation this species with the test on is less ornate than spinicostata 

 with the test off. The latter was evidently strongly knobbed to about 210 mm. 

 diameter ; in this species the knobs are very feeble at 85 mm. diameter. In sep- 

 tation there is but a slight difference ; in spinicostata the terminal lobule of L is more 

 anisosceloid, and the lateral lobules are anisometric. 



Sonninia spinea occurs in the Concavum-zone at Bradford Abbas. It is illustrated 

 in PL LXXXVI : fig. 4, side view ; fig. 5, outline front view ; fig. 6, suture-line. 



Sonninia submarginata, 8. Buckman. See Plate LXXI, figs. 1 — 3, and page 329. 



Add to description : — Suture-line latilobate, L with slightly anisometric lateral 

 lobules, terminal lobule intra-axial, anisosceloid, inequicellate. 



Sonninia substriata, 8. Buckman. Plate CIII, figs. 12, 13. 



See Plate LXX, figs. 6, 7 ; Plate LXXI, figs. 6—8 (and ? Plate LXXII, 

 figs. 1, 2), and page 330. 



Add to description : — Suture-line of the type shows a broad, asymmetrical L, 

 the terminal lobule anisosceloid, intra-axial, inequicellate, the lateral lobules aniso- 

 metric. 



Characters similar to the above are shown by the suture-lines of two other 

 specimens (PI. LXXI, fig. 8 ; PI. CIII, fig. 12). The L of the type seems to 

 indicate septal degeneration, but it is not in a good condition for being traced. 



So far as the septation is concerned this species seems to agree fairly with 



