116 G. LINDSTKÖM, ON THE SILURIAN GASTROPODA AND PTEROPODA OF GOTLAND. 



wliicb is tlie sloping, interiör uiiibilicul sido and tliu both equal sides are tbe exteriör 

 and tbe apical sides. Tliere is tbus a narrow ridge rnnning along tbe niiddle of the 

 nnibilieal side, being in older wborls as thiii as a knite edge. The ornanientation con- 

 sists of transversal, regiilarly distantiatcd, narrow lines, somewbat Avavy and enclosing 

 between tbem nuineroiis, ininute lines, parallel witb tbem. VVben reacbing tbe wirig 

 of the slit band they are bent in a gentle curve backwards. On the uiubilical side 

 tbe seulpture is tnore coarse and consists of imbricated lamellai. 



Length of wborl and slit band near the aperture 21 millim. Lengtb of slit band 

 alone 10 millim. Breadth of whorl near the aperture 10 millim. 



Only one specimen bas bitherto been found in a detached stone on the shale 

 beds near Wisby, which probably, as far as can be judged by the rock, belongs to the 

 Upper Silurian of Gotland and the oldest shale. 



This species is related to Eccyliomplialus alatus Ferd. Roemer Letb. Geogn. 1876, 

 tab. 5 fig. 5, in which, bowever, the airical spire is elevated into an apex on the urn- 

 bilical side, the slit band is shorter and the section of the wborls is ratber more oval 

 than triangulär. E. alatus or a nearly related species also occurs in the Upper Red Or- 

 thoceratite limestone of Öland, while another, which comes near to Pleurotomaria repli- 

 cata, bas been found in tbe Upper Gray limestone of Dalecarlia. These fossils have 

 been numbered witb Eccyliomphalus, but I shall further down attempt to show that 

 this genus caunot be retained, as it contains either evolute Pleurotomarias as this 

 species and kindred, or evolute Euomphali, the peculiarity of tbe uncoiled whorls being 

 in no way any cliaracteristic sufficient enougb for generic distinction, when taken alone. 

 This Pl. replicata is a direct development from such forms as those described with 

 Pl. qualteriata and connects tbem with the group Alataj, being probably in genetic 

 connection with the fourtb of these Qualteriataj. 



28. Pleurotomaria alata Wahlenberg. 



Pl. X, fig. 18—32. 

 Cornu Araraoiiis laevis vestigium. 1730 Bromell, Lithogr. Svec. in Act. liter. Scient. Svec. p. 31. 



Turbiuites alatua 



Turbo äiaius 

 Delpliinula alata 



Euomphaliis alatus 



1818. Wahlenberg Petref. Svec, 69. tab. Ill f. 6—8. 



1828. HisiNGEK Aiiteckn. IV, 221, 237. 



1824. KöNiG Icoiics Ibasiliura sectiles, pl. IX fig. 107. 



1829. HisiNGER Tablcau ed. 1, 10. 

 1831. Id. Anteckn. V, 113. 



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



1829. Brongniart Tableau des tcrrains, 428. 



1837. HisiNGER Lethjea, 36, tab. XI f. 7 a— b. 



1839. Angelin Museum Palseoutologicum Scandiuav. N:o 30. 



1839. SowERBY Sil. Syst., 631, pl. 13 f. 28. 



1841. HisiNGER Förtecku., 55. 



1843. Morris Brit. Fossils, Ed. 1, 144. 



1847. MURCHisoN Quart. Journ. Geol. Soc, 29. 



1848. Bronn Noraenclator, 478. 



1848. Phillips Mem. Geol. Survey II, i, 356. 



