KONGL. SV. VKT. AKAIJEMIENS IJANDL. BANJ). 19. N:0 6. 75 



on which it rests. The umbilicus is vvide and open in the young spcciinens; in the 

 older it beconies by degrces more and niore narrow, and is at last so concealed by 

 the large corners of the aperture and the interiör lips, which have grown över it, that 

 only a little space is left open. 



x\s 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 sliaped 

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

 trace of the crescent shaped lines of growth is effaced. The height of this keel sorae- 

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



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

 interiör 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 

 lamella?, through which clearer spaces or tubes vertically penetrate, pl. VII f. 9. 



Colouies 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 Wisby, in the 

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



2. Belleroplion fasciatus n. 



Pl. VI ligs. 13—14. 



Shell globular, the transverse striaB 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 stånd oiit 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 exteriör or superior margin with an acute angle and the interiör 

 one arched. Seen from the aperture the shell presents an obovate oiitline. 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. spha^ra, but 

 differs through its obovate outline and the transverse striaj, Height 25 n)illim., 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. Belleroplion globulus n. 



Pl. v figs. 25—34. 



Shell of somewhat variable form, globular, ovate or elliptical in outline, sui'face of a 

 dark, glossy hue, almost sraooth, with extremely fine, densely packed transverse strias, which 



