54 DEVONIAN FAUNA. 



2. Genus — Rhaphistoma, Ball, 1847. 



These are small low shells, with a rather small uml^ilicus, which often bears a 

 small marginal keel. The mouth is sub-trigonal. The whorls bear a narrow 

 band produced by a sinuosity in the aperture. The surface shows growth-lines 

 or fine crenulations at the suture. It occurs in the Lower Silurian and the 

 Carboniferous, and de Koninck remarks on its supposed absence from Upper 

 Silurian and Devonian rocks. 



It has generally been regarded as belonging to the Pleurotomariidae, ; but 

 de Koninck, and perhaps Hall, are inclined to class it with the Solariidae. 

 Possibly it really goes to show the relationship between these two families. 



Fischer ^ regards it as synonymous with Scalites, Conrad, 1842. 



1. Rhaphistoma junius, de Koninck. Plate VI, figs. 5 — 7. 



? 18J)1. Pleceotomaeia expansa, Phillips. Pal. Foss. (not Geol. Yorks.), p. 97, 



pi. xxxvii, fig. 179. 

 1843. EuoMPHALUS EADiANs, de Koninch (pars). Dese. Anim. Yo&s. Carb. Belg., 



p. 442. 

 1854. — — Morris. Catal., p. 248. 



1876. — — Armstrong, Young, and Rohertson. Catal. West Scot. 



Foss., p. 56. 

 1881. Raphistoma jtjnioe, de Koninch. Ann. Mus. Eoy. H. N. Belg., vol. vi, 



p. 135, pi. xii, figs. 15-17. 



Description. — Shell very small, sub-conical, but so much depressed as to be 

 nearly discoidal. Spire consisting of about five rather slowly increasing volutions, 

 much enveloped, the lower walls covering nearly half of the upper half of the 

 whorl above. Apex elevated, sharp. Suture slight, facing upwards. Whorls, in 

 section, much wider than high ; in outline, turning suddenly outward from the 

 suture and spreading out obliquely and almost flatly to the centre of the back, 

 where they curve round so suddenly as almost to form a blunt rounded angle, and 

 then proceed with a slight convex curvature to the umbilicus. Ornament consist- 

 ing of a row of strong, short, transverse ridges, close to the suture, which vanish 

 immediately ; the rest of the surface showing no ornament except occasionally 

 very slight and indistinct continuations of some of the striae of the sutural crown, 

 which arch backwards, and then perhaps turn suddenly forwards just above the 

 angle of the back. Umbilicus small, bordered by a small sunken keel. 



Size.' — Height 4 mm., width 7 mm. 



Localities. — A specimen from Pilton is in the Porter Collection ; three others 

 • 1887, Fischer, ' Manual Conchyl.,' p. 851. 



