﻿SONNINIA SPINIFERA. 



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twenty years ago, and it has attracted my attention for considerably more than half 

 that period. It has always been regarded as a very rare and distinct form ; and 

 I can certainly confirm its rarity, for had there been any duplicate among the 

 thousands of specimens which have come under my notice I should certainly have 

 detected it — its peculiar form could not fail to attract my attention. 



The specimen came from the Concavum-zone of Bradford Abbas — from that 

 justly-celebrated opening at East Hill which, by its long association with my 

 father, came to be known as " Professor Buckman's quarry." 



The side view of the upper half of this grand fossil has been depicted in 

 Plate LXXII, fig. 3 ; the front view in fig. 4 ; part of the suture line in fig. 5. 



Sonninia spinipera, S. Buchman. Plate L, figs. 14, 15. Plate LXXIV, figs. 



4—6. 



Discoidal, compressed, carinate. Whorls, in section, sub-elliptical, 1 ornamented 

 first with regular spines, later with spines parted by one, two, or more ribs, 2 later 

 still with direct, much reclining, not prominent ribs, for the most part lost on the 

 outer third of the whorl, which carries only ventrally-inclined growth-lines. 

 Ventral area arched, divided by a small, presumably hollow, carina. No inner 

 margin. Inclusion about one-third. Suture-line with an unsymmetrical superior 

 lateral lobe, the outer lobule being rather exaggerated. 



The strongly-reclining ribs bring this species into connection with the 

 aca iithodes-stock ; but from the small size to which it attained, the small spines, 

 and the want of elaboration of the ribbing, it does not seem possible to derive it 

 from members of that group. Looking at the specimen figured in Plate LXXIV, 

 figs. 4 — 6, as an adult form, a separate derivation from multispinata seems more 

 probable, the ornaments and the shape of the young (Plate L, figs. 14, 15) 

 certainly supporting this view. Should it, however, be found that spinifera is the 

 young of a much larger fossil, derivation from acanthodes or from ptycta might 

 appear possible ; but at present there is the evidence of one feature at least 

 against such derivation, namely, in spinifera the obsolescence of the ribbing on the 

 outer third of the whorl. This character seems to separate it altogether from the 

 members of the aca nthodes-stock. 



1 In youth, ventrally-expanded, subquadrate — that is, somewhat of quadrate shape, but the 

 ventral side broader than the dorsal. The fig. 15 of PI. L represents this at the bottom ; but the 

 aperture is not quite correct, and the extra matrix on one side gives a false impression. The 

 aperture is rather too long ; and from spine to spine the ventral area should be broader and flatter. 



2 Up to about ii mm. diameter. 



