438 INFERIOR OOLITE AMMONITES. 



the embraced whorl. In the matter of suture-line, however, there is a marked 

 difference. The siphonal lobe has its terminal lobule deeply divided, a feature 

 wanting in modesta ; and the inner lobule of L in this species is proportionately much 

 more developed than in that one ; the terminal lobule is isosceloid and less intra- 

 axial, the outer lobule is more deeply divided into two more equal parts. 



In general details the suture-line agrees fairly with that of immature dominans. 

 The outer lobule is similarly bipartite, but it is scarcely so large — especially the 

 lower branch. The agreement in septation, however, seems close enough to justify 

 the supposition that loculosa may be the retrogressive descendant of dominans. 



Bonn, loculosa, is from Bradford Abbas. Part of its side view is depicted in 

 PI. XCII, fig. 5 ; its whorl-section, fig. 6 ; its suture-line, fig. 7. 



Species innominatx. 



Sonninia, sp. Plate CIII, fig. 24. 



1892. Sonninia dominans. This Monograph, Plate LXVII, figs. 1, 2, p. 322 



(pars). 



This fossil has considerable external resemblance to Sown, dominans type, but 

 it is rather less costate, while the costas are regular, and by no means connate. 

 The septa agree fairly with those of dominans — at any rate, they show that the 

 fossil belongs to the longilobate section, namely, II, D, B, p. 391. The length 

 of the septa separates the form from Sonn. revirescens. Comparison with fig. 1 of 

 PI. XCIV will show that it is now separated from Sonn. dominans on account of 

 the difference in costation mentioned above. 



Sonninia, sp. Plate CIII, fig. 20. 



See Plate LXVII, figs. 3—5. 



The external appearance of the fossil shows most likeness to Sonn. reuovata, 

 juv., PI. XCIII, figs. 4 — 6, but it is less spinous, and the whorls are somewhat more 

 compressed. The septa, 1 however, differ, for the terminal lobule of L is not so 

 anisosceloid ; the lateral lobules are consequently more opposite, and they are 

 also distinctly shorter. There is a likeness to Sonn. alternata ; but the costae are 

 more regular in size, and the septa are very different : in this form the terminal 

 lobule of L is much less anisosceloid, the lateral lobules are nearly opposite and 



1 Owing to breakage of the fossil the upper boundary of the superior lateral saddle of the upper 

 septal margin (PI. LXVII, fig. 5) is incorrectly shown by the specimen. A more precise delineation 

 is given in PI. CIII, fig. 20, with supplementary details. 



