158 G. LINDSTRÖM, ON THE SILURIAN GAöTROPOUA AND PTEROPODA OF GOTLAND- 



Turbinites cornu arietis 

 Delphinula cornu arietis 



Euomphahts cornu arietis 



Straparollus cliscors 

 Turbo cornu arietis 

 Polytropis cliscors 



1839. Sow. Sil. System, 626 pl. 12 f. 18. 



1843. MoKKis Catal. Brit. Foss., 144. 



1847. MuRCHisoN Qu. Journ. Geol. Soc, 29. 



1848. BiioNN Nomenclator, 479. 



1854. Morris Catal. 2d Ed. 247. 



1855. Mac Coy Palreoz. Foss. 298. 

 1868. Fr. Schjiiut Estland, 204. 



1859. Salter in Siluria 3d Ed. 548, pl. 24. f. 12. 



1867. Lindström Nomina, 23. 



1873. Salter Catal. Cambr., 156. 



1818. WahlExNbeeg Petref. Suec, 68, pl. III fig. 9, 10. 



1828. His. Anteckn. IV, 257. 



1829. His. Tabl. 10. 

 1831. Id. Tabl. ed. 2, 8. 

 1831. Id. Anteckn. V, 113. 



1837. Id. Leth. Suec, 36, tab. XI fig. 6. 



1841. Id. Förteckn., 55. 



1848. Bronx Nomencl., 479. 



1858. Fe. Schmidt Estland, 204. 



1867. Lindström Nomina, 23. 



1850. D'Orbigny Prodr. I, 29. 



1850. Id. ibid., 30. 



1881. De Kon. Faune Carbon. Belgique. II.iii, 107. 



Shell discoid, spire short, or, in the variety called E. cornu arietis by Wahlen- 

 BERG, prominent, with six whorls, which are carinated on their inferior surface by 

 blunt, longitudinal keels of varying number and prominence, from three to eight in 

 the typical form. In the elongated variety there are three on the inferior surface, 

 but as many as eight on the umbilical one. The surface slopes from the lowest 

 keel towards the suture which is shallow. The keels are crossed by narrow, trans- 

 verse, undulated lines of growth, giving the surface an imbricated appearance. The 

 transverse striaj of the umbilical surface are curved sigmoidally and have grown out into 

 thin, prominent lamellse. The great amount of variation as to the ornamentation in 

 these shells may be gathered from the numerous figures given. The aperture is trans- 

 verse, its superior margin sigmoidally bent, the outer lip thin and notched or angu- 

 lated where the keels are formed, the inner lip is thick. The umbilicus is wide and 

 open and all whorls are visible. H. 23 mill. br. 73 mill. 



It occurs at Länsa on Fårö, at Wialmsudd on Fårösund; in the upper limestone 

 beds of Wisby and in the shale of Wisby and rnost plentifully at Westergarn. 



In the variety »cornu arietis» the umbilicus is relatively less wide and the course 

 of the strise on the umbilical surface is more straightly directed backwards. The 

 aperture is also more circular. H. 28 mill., br. 39 mm. Largest diameter of the aper- 

 ture 16 mill. It has been found at Länsa and Lutterhorn in Fårö, also at Alnäse by 

 Prof. P. T. Cleve, in the crystalline limestone of Wialmsudd, in the canal near West- 

 öös in Hall, Samsugn in Othem, Follingbo, Bara, Kristklint in Kapellshamn, Hörsne, 

 Martebo, in Kyrkberget in Wisby, at Walve ref, Westergarn and Klinteberg, thus chiefly 

 n the higher strata. The rule holds good in these, as in so many others, that the 

 spiral ridges are more prominent in small specimens or on the old whorls of the larger 

 ones and are apt to disappear on the larger and younger whorls. 



