KONGL. SV. VET. AKADEMIEN.s IIANUL. liANJ). 19. N:0 6. 75 



on which it rests. The umbilicus is wide and open in the young specimens; in the 

 ohler it becomes by degrees more and more narrow, and is at last so concealed by 

 the large corners of the aperture and the interior lijjs, which have grown over it, that 

 only a little space is left open. 



As far as may be judged by the direction of the lines of growth there has been 

 a deep and acuminate sinus in the outer lip. The slit band is comparatively narrow 

 and sunk between two faintly elevated lines and covered by distantiated crescent shaped 

 lines of growth. On the last whorl it changes into an elevated keel, on which every 

 trace of the crescent sha])ed lines of growth is effaced. The height of this keel some- 

 times amounts to more than one millimeter above the surface of the whorl. 



The thickness of the shell is much variable, generally thin, excepting along the 

 interior corners of the aperture, where it covers the umbilicus and is several millime- 

 ters thick. The shell, in a thin section under the microscope, shows very thin, wavy 

 lamelliv, through which clearer spaces or tubes vertically penetrate, pi. VII f. 9. 



Colonies of a bryozoan, a Ceramopora, have often covered large specimens of this 

 shell with their luxuriant growth and in all probability destroyed the shell, which has 

 been dissolved, as only a cast of its surface is left on the calcareous basis of the Ce- 

 ramopora. 



Largest diameter 96 millim., breadth of aperture 65 millim., height of the same 

 55 millim., diameter of umbilicus 15 millim. 



This shell has been found very common in the lowest shale near \\'isby, in the 

 superjacent limestone beds at Wisby and Martebo and also in the shale beds at Petesvik. 



2. Belleroplion fasciatus n. 



PI. VI tigs. 13—14. 



Shell globular, the transverse striae of the surface are in regular distances, with 

 smooth, equal, band like interstices. They join the slit band in an angle of 66° and 

 then stand out from the band nearly horizontally. The slit band is sunk and narrow. 

 There are only three whorls visible, but probably they are at least four. The aper- 

 ture is cordate, the exterior or superior margin with an acute angle and the interior 

 one arched. Seen from the aperture the shell presents an obovate outline. The um- 

 bilicus is closed by a fold of the margin of the lowest apertural corner. 



Of all the Gotland Bellerophons this is most nearly related to Bell, sphtvra, but 

 differs through its obovate outline and the transverse striie. Height 25 millim., breadth 

 16 millim., height of aperture 10 millim., breadth 16 millim. 



Only four specimens have been found in the middle limestone beds (b) and the 

 lowest part of c, near Wisby and Kyrkberget in Wisby. 



^ 3. Bellerophon globulus n. 



PI. V rtgs. 25—34. 



Shell of somewhat variable form, globular, ovate or elliptical in outline, surface of a 

 dark, glossy hue, almost smooth, with extremely fine, densely packed transverse stri;\3, which 



