140 G. LINDSTRÖM, ON THE SILURIAN GA8TROP0DA AND VTEROPODA OF GOTLAND. 



2. Euomplialus triquetrus n. 



Pl. XIII, tig. 32—35. 



Shell discoid, of ti^iangiilar section, with four whorls, of which the older are 

 contiguous and the body whorl free through almost its whole leiigth, rapidly wideiiing, 

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

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

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

 On the interiör 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 Jargest, nearly flat, and the two other shorter sides meet in an obtuse 

 angle on the apical side. The aperture is transversally triangulär, 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 triangulär, fig. 35, 

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

 meter of the shell 51 mm. 



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

 Westkinde and Hogrän. 



^b'- 



3. Euomplialus tuba n. 



Pl. XVIII %. 6—8. 



Shell globular, with a low, though prominent spire 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 

 ornaraentation consists in narrow longitudinal threads, which are crossed by indistinct, 

 transverse lines of growth, coarser and flner, forraing 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 limestone of Samsugn in Othem. A nucleus from 

 Martebo of lai'ger dimensions may possibly also belong to this species. 



4. Euomplialus prsecursor n. 



PI. XVIII, fig. 9—11. 



Shell discoid, spire moderately prominent, of tive 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 flat 

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



