GONIATITES. 71 



9. GoNiATiTES ciECUMPLBXiFER ?, Sanclherger. PI. VI, fig. 17. 



1851. GoNiATiTES ciRCUMFLExiFEB, Saudherger. Verst. Ehein. Nassau,]). Ill, 



pi. xi, fig. 8. 



Description. — Shell small, involute, apparently globose. Umbilicus small, con- 

 sisting of a hollow spire, with a rounded thread formed by the inner margins of 

 the successive whorls. Sides of whorls rising inwards, and rounding abruptly to 

 form this thread, and then becoming gently convex so that their deepest part is 

 at some distance from the centre. 



Size. — The only specimen is too incomplete for measurement. 



Locality. — Barton. A single fragmentary specimen in the British Museum. 



Remarks. — This small fossil appears to me to difier from the other British 

 Middle Devonian Goniatites. Its umbilicus is formed on quite a difi'erent principle 

 from that of G. nuciformis, being more in the shape of a screw with a sharp spiral 

 thread separating a shallow concavity, and round its border the convex whorls 

 are definitely depressed. 



G. circumfiexifer, Sandberger, is a small species, that might be exactly repre- 

 sented by the present defective specimen, which has no trace of either suture-lines 

 or surface-marks, and which is rather less than half of a perfect shell, so that the 

 form of its back cannot be exactly ascertained. I have therefore only provisionally 

 identified it with this German species, which its describer appears to separate 

 from his G. retrorsiis, von Buch, on account of the large size and convexity of its 

 lateral lobes, though some of the suture-lines which he gives of the latter species 

 appear to have the same character. 



Affinities. — This shell does not seem to be at all in the nature of G. linearis, 

 Miinster,^ with which it has been identified in the museum lists, but it much more 

 nearly resembles a small form of G. orhicularis, Miinster,^ except that its umbilicus 

 is larger and that its size is so very much less. The latter shell was first regarded 

 by Miinster as a variety of G. Mimsteri, von Buch,^ but was afterwards separated 

 from it by him on account of its greater rotundity, &c., in which respect it is more 

 like our specimen. I am not, however, inclined to see more than a variety of 

 von Buch's species in that of Miinster. Sandberger* figures a fragmentary 

 example of G. Mimsteri, von Buch, which shows the suture-line, but gives no data 

 for comparison with our fossil ; but he afterwards separates this as a distinct 



1 1832, Miinster, ' Uber Clym. und Gon. Fichtelgeb.,' p. 22, pi. va, tig. 1. 

 3 1832, ibid., p. 20, pi. va, figs. 4«— c. 



•^ 1832, von Buch, ' Uber Amm. und Gon.,' p. 41, pi. ii, fig. 5, and 1832, Miinster, ' Beitr.,' pt. 1 

 Supt., p. 19, pi. V A, fig. 3. 



* 1851, Sandberger, ' Verst. libein. Nassau,' pi. v, fig. 2. 

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