76 G. LINUSTUOM, ON THE SILUKIAN GASTKOl'ODA AND I'TEKOl'l iDA OF GOTLAND. 



join tlie slit band :it an an^le of 38°; tliey bend outwards towards the sides and a^ain 

 converge towards the umbilicus. The slit band forms an elevated keel with a flat top, 

 on each side bordered bv a fine line and wavy with the minute and delicate lines of 

 jrrowth. Whorls four and a half, regularly inci'easing in width, twice as large as high 

 and consequently not so narrow as in Bell, spha^ra. Shell thick and as common in 

 tliis genus, at thickest around the umbilicus and at the inferior corners of the aper- 

 ture. The last whorl, when seen from the side, is straight or only faintly curved, and 

 its apertural and dorsal contours are nearly parallel, f. 2(i. In my specimens, which 

 arc not quite couiplete, the aperture is longer than the I'cst of the shell. The infe- 

 I'ior corners of the aperture near the umbilicus, where the shell is at thickest, are 

 rounded or cylindrical and completely hide the umbilicus, which in young specimens 

 is oi)en. Diamet. 20 millims., breadth at the fragmentary aperture 17 milliins., height 

 of the a[)erture 7 millini. 



Occurs in the shale beds of Eksta at Djui)vik and in Frojcl. It is nearly related 

 to Bell, sphiera, but differs by having the umbilicus entirely covered by a fold of the 

 retlexed border of the apertui'e. The shell is moreover thicker and the direction of 

 the transverse striie and their angle when joining the slit band quite different. 



4. Bellerophon taenia n. 



Pi. Vi ligs. 22—25, pi. VII tigs. 4—5. 



Shell discoid with six much compressed and thin whorls, transverse, nearly el- 

 liptical in tlieir section, twice as bi'oad as high, their dorsal side only a little convex? 

 in many nearly Hat, the lateral angles very thin and acute. All whorls are visible 

 on the umbilical as well as on the apical side. The only specimen which shows 

 some fragments of the expanded aperture makes it not clear whether there has 

 been an open or closed umbilicus, but it seems likely that it has been more narrow 

 than may be judged of by its wideness in the other samples. At the aperture, which 

 seems to have been quite as large as in Bell, sphajra, the shell attains its greatest 

 thickness and consists of several sti'ata. On other parts, where fragments of it still 

 are seen, it is very thin. The transverse striae of the surface are nearly straight or 

 only faintly curved in an angle of 68° near the slit band. This band is narrow and 

 only a little elevated between two sharpedged lines. Height 60 millim., breadth of 

 aperture 60 millim., breadtii of the last whorl near the aperture 28 millim., height 19 

 millim. Occurs in the lower limestone beds at Ostcrgarn and Ardre, and also on 

 the shore of Hammar in Krilklingbo, and in the soft gray limestone of Lindeklint and Frojel. 



5. Bellerophon fastigiatus n. 



PI. VI, ligs. 1—10. 



Shell rather more discoid than globular, ajjcrture transverse and triangular in outline, 

 the base being only slightly arched. It is incomplete, the mai-gins broken off and 



