SONNINIA MARGINATA. 407 



Sonn. submarginata. The lateral lobules are rather more anisometric, due to the 

 abbreviation of the inner lobule, which, however, is a feature in the catagenesis of 

 these series. 



The specimen described as an intermediate form (PI. LXXII, figs. 1,2) maybe 

 considered near to this species until septal evidence to the contrary be forthcoming. 

 It is on the whole similar in external appearance. 



The submarginata-stock was considered to have sprung possibly from 

 8. marginata (page 329), and the septal evidence now adduced has not altered this 

 opinion very materially. It suggests, however, that Sonn. spinicostata and the new 

 form, Sonn. spinea, belong here, that subcostata should be removed, and that 

 8. marginata is a close ally in a slightly different genetic series. 



B. L scarcely so short and broad-stemmed. 



Sonninia nodata, S. Buchman. See Plate LXXXIX, figs. 1 — 5, and page 369. 



Add to the explanation of the Plate (fig. 4), " Bradford Abbas, my 

 Collection." 



Sonninia marginata, 8. Buchnan. Plate XCVI, fig. 6. 



See Plates LXII, LXIII, fig. 2, and LXV, figs. 1 and 2, and page 321. 



From this species exclude the form figured in PI. LXIV (see Sonn. regularis). 

 Add to the description : — The suture-line has somewhat broad-stemmed lobes, 

 L with intra-axial, anisosceloid terminal lobule, the lateral lobes isometric. 



Of the specimens figured the smaller example (PI. LXV, figs. 1 and 2) is slightly 

 less spinous than the larger shell. In the printing of PI. LXV the young form 

 has obtained an appearance as if the costse of the last half-whorl were slightly 

 nodate, or perhaps subbullate. This, however, is incorrect ; the ribs are slightly 

 elevated in the middle, but the elevation is so gradual that nothing like a bulla is 

 produced, still less is the shell nodicostate. The only feature of the former kind 

 is seen just after the spinous stage : here, at distances apart equal to the former 

 interspinous spaces, are two or three feeble sub-bullas. 



The septa suggest the present position of S. marginata. 



