168 G. LINDSTROM, ON THE SILURIAN GASTROPODA AND PTEROPODA OF GOTLAND. 



horizontal, triangular. The contour of the Avhole operculum is also more cj^lindrical. 

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

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



Oriost. \^'isbyense has been found in the middle limestone sti'atum of Wisby and 

 at Kalens Qvarn. 



9. Orio stoma angulifer n. 



PI. XX fis:. 17—21. 



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

 the lower surface of which forms the spire into an evenly sloping cone, intersected by 

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

 the bod}' whorl, one near the sutural groove, one a little below the median line of 

 the whorl and one around the umbilicus. Between the two later 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 strife. 

 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 Roemeri n. 



PL XVIII f. 22—29. 



Euomphalus cornu arietis 1838. Angelin Museum Palseont. Svecic. JVJ 10. 

 Euoiiiphalus funatus 1867. Lindstrom Nomina, 23. 



1876. Ff.rd. Roemer Letli. Geogn. Atlas pi. 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 with them. They 

 continue without interruption close to the suture, without 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 laminaj. These 

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

 gether, only as lamellar 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 i)artially hidden by the reflexed border 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 interior nacreous coating are seen. H. 30 mill., br. 36 



