168 G. LINDSTRÖM, ON THE SILURIAN GASTROPODA AND TTEROrODA OF GOTLAND. 



horizontal, triangulär. The contour of the whole operculum is also mure cylindrical. 

 The inside is a little inore deepened than in the others. The shell to which it has 

 belonged is not yet known. H. 8 rnilL, br. 8. mill. 



Oriost. Wisbyense has been found in the middle limestone stratum of Wisby and 

 at Kålens Qvarn. 



9. Oriostoma angulifer n. 



Pl. XX fig. 17—21. 



Shell turbinate, globular with moderately elongated spire, of six angular whorls, 

 the lower snrface of -which forms the spire into au evenly sloping cone, intersected by 

 the narrow and deep suture. There are from three to four fine and acute keels on 

 the body whorl, one near the sutural groove, one a little below the median line of 

 the "whorl and one around the umbilicus. Between the two låter there are on smal- 

 ler specimens one more and indications of yet smaller ones. The transverse striation 

 of the surface is microscopically minute and consists of nearly vertical, straight stria3. 

 The aperture is polygonal, higher than broad with thin lips. The umbilicus is wide 

 and open. H. 6 mill., br. 8 mill. 



Six specimens have been found in a soft, gray limestone from a canal near Her- 

 revik in Ostergarn. This little shell comes near to Or. Wisbyense through its few 

 keels and the deep umbilicus and also reminds of Oriostoma angulatum with its an- 

 gular contour, fine ornamentation and deep suture. 



10. Oriostoma RcBmeri n, 



Pl. XVIII f. 22—29. 



Euomphaliis cornu arietis 1838. Angelin Museum Palaeont. Svecic. JV? 10. 

 Euomphalus funatus 1867. Lindström Notnina, 23. 



1876. Ferd. Eoemer Letli. Geogn. Atlas pl. 14 f. 12. 



Shell turbinate, globular, with six ventricose whorls. The longitudinal ornamen- 

 tation predominates entirely and the surface is consequently covered by chord like 

 keels, going close from the suture to the umbilicus, as many as 43 in some specimens. 

 They are all nearly of the same size, only a few narrow are mingled Avith them. They 

 continue without interruption close to the suture, Avithout there leaving any zone free. 

 The transverse striation is visible as scaly, crescent like indentations on the revolving 

 lines, which sometimes are as if cut up in a great number of thin laminas. These 

 transverse imbrications vary much as to proximity and shape, being, when close to- 

 gether, only as lameliar crescents, when more wide apart, as longitudinal tubes, cone 

 in cone shaped. There are no ridges around the umbilicus, more elevated than the 

 other ridges. The umbilicus is narrow and partially hidden by the reflexed börder of 

 the inner lip. The aperture is circular and both lips are thin. The shell is very thin 

 and it is almost impossible to find a specimen which is not crushed or distorted. On 

 the nucleus fine traces of the interiör nacreous coating are seen. H. 30 mill., br. 36 



