130 r,. LINDSTKOM, ON THK SILURIAN GASTUOPOTIA AND PTEROPODA OF GOTLAND. 



The apex of the spire is in all specimens, which have been investigated, filled 

 up with solid calcareous spar of a brownish colour, Avithout any trace of transverse 

 diaphragmata. The nuclei have a glossy surface and look as if the interior walls of 

 the shell had been porcellanous. The slit band is prominent a little above the middle 

 of the whorls, it is narrow and slightly concave along its median line- The aperture 

 is rather obovate approaching to the circidar. The umbilicus seems to have been 

 large and open as shown by longitudinal sections when there is no compact columella 

 (fig. 18), but an open tubular axis interiorly. 



Very frequent in the inferior limestone of Ostergarn at Grogarn and Katt- 

 hammarsvik, but almost only as nuclei, on which traces of the sculpture of the shell 

 are visible. It has also been found in the neiohbourinor strata of Kriiklin<i;bo and 

 Ardre, and it is probable that some nuclei from the limestone of Wisby belong to 

 this species. 



Height 80 millira., breadth 21 mill., apical angle 22 °. 



This common species has usually been confounded with Murch. cingulata, as 

 HisiNGER himself did, till he in his nFOrteckning ofver Svenska petrificater", edited 1841, 

 p. 56, separates it from M. cingulata, without giving it any new name. 



7. Murcliisonia attenuata Hisingek. 



PL Xir fig. 20—24. 

 Turbinis maiini nucleus lapideus l.TJvis etc. Bromell Act. Lit. Siiec. 17.38 vol. Ill p. .37. 



Turritella attenuata 1840. His. Letli. Suec. Supplera. Secundum, 4. tab. 37 f. 7. 



1841. Id. Forteckning, 56. 



1848. Bronn Noraenclator, 1.331. 

 Murchisonia attenuata 18G7. Lindstrom Nomina foss. Gotl., 23 (ncc. Murcliisonia attenuata Hai.l 18r)6, 



Trans. Albany Instit. vol. IV, 27). 



Shell elongate, whorls seven in the most complete specimens, though there have 

 certainly been many more. The whorls are ventricose, nearly as long as broad, some- 

 what angular where the slit band is projecting. This band is narrow, placed a little 

 below the median line of the body whorl and quite on the middle line of the other 

 whorls. It has an even surface, fig. 24 section, the crescents are regular, fig. 23. 

 But near the aperture in large specimens the transverse ornamental strias above and 

 beneath are confluent with the band without any separating or bordering lines and 

 it continues only as an elevated ridge, sometimes not clearly distinct from the 

 surface. In this feature it shows relations to such genera as Euomphalus and 

 Loxonema (for inst. pi. XV fig. 9) and also to Pleurot. planorbis His. The shallow 

 suture crosses the longitudinal axis in a line more oblique than in the other species. 

 There is no umbilicus and the aperture is oblong, the ujjpermost corner acumi- 

 nated, its columellar lip thin, reflexed. Height 51 millim., width of body whorl 

 18 millim. 



