140 G. L1NDSTR6M, ON THE SILURIAN GASTROPODA AND PTEKOPODA OF GOTLAND. 



2. Euomplialus triquetrus n. 



PI. Xlll, lig. .•52— 35. 



Shell discoid, of triangular section, with four whorls, of which the older are 

 contiguous and the body whorl free through almost its wliolc length, rapidly widening, 

 much more so than in E. Gotlandicus and it is broadly expanded at the aperture. 

 The three smaller whorls, which form the apex, are lilled with a homogenous, cal- 

 careous deposit, only interrupted by a transverse diaphragma in the second whorl. 

 On the interior side of the umbilical surface the nucleus of the body whorl has a 

 shallow, longitudinal groove, being the impression of some internal ridge. The um- 

 bilical side is the largest, nearly flat, and the two other shorter sides meet in an obtuse 

 angle on the apical side. The aperture is transversally triangular, broader than high, 

 the inferior corner acuminated. It is oblique and the superior lip more prominent 

 than the inferior one. The notch in the inferior lip is broadly triangular, fig. 85, 

 and deeper than in the preceding species. H. of aperture 16 mm., br. 22 mm., dia- 

 meter of the sliell 51 mm. 



Specimens have been obtained from the shale and limestone of Slite, from Boge, 

 Westkinde and Hogran. 



3. Euomphalus tuba n. 



PI. XVm fig. 6—8. 



Shell globular, with a low, though prominent si)ire and four tubular whorls. 

 They are ventricose, with slightly elevated ridge in continuation of the apertural in- 

 dentation. The suture is deep and the whorls sink much abruptly towards it. The 

 ornamentation consists in narrow longitudinal tiireads, which are crossed by indistinct, 

 transverse lines of growth, coarser and finer, forming an obtuse angle in the same 

 line as the slit is situated. The aperture is circular and the lips thin, the umbilicus 

 is narrow, but open. 



H. 7 millim., br. 10 m. 



A single specimen from the liniestone of Samsugn in Othem. A nucleus from 

 Martebo of larger dimensions may possibly also belong to this species. 



4. Euomplialus prsecursor n. 



PL XVIIl, tig. 9—11. 



Shell discoid, spire moderately prominent, of five whorls, rapidly increasing in 

 size, the body whorl in breadth surpassing all the others. The narrow characteristic 

 keel is seen a little below its median line, having inside it towards the suture a fiat 

 surface. On the umbilical side of the body Avhorl there is a narrow, sharp keel nearer 



