114 G. LINDSTKUM, ON THE .SILURIAN (iASTKoI'ODA AND I'TEROl'ODA OF GOTLAND. 



which I)r G. J. IIindk kindly has sent me <a cast to comi)ar(!. It has often been 

 confounded witli Pleurot. baU.eata Phillii's whicli is a quite different species, as I liave 

 learnt also through a cast kindly sent from Dr Hinde. 



26. Pleurotomaria limata nom. nov. 



PI. X tig. 2—17. 



Euomphalus carhiafiif 1839. Sowerby in Sil. Syst.. 616, pi. (5 f. 10. 



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



1847. MuRCHisoN Silurian liocks of Sweden, Qu. .Toiirn. Geol. Soc. Lond., '29, 49. 



1854. Morris Catal. 2:d Ed.. 247. 



1867. Salter Siluria 3:d Ed., ."JSl, pi. 24 f. 11. 



1873. Id. Catal. Cambridge Foss., 157. 



Straparollus carinatus 1850. D'Orb. Prodr. I, 29. 



Shell globular with short spire or turbinated with elongated spire and ventri- 

 cose whorls. The former variety, tigs 2 — 6, is from the southern localities of Gotland, 

 mentioned below, the later, figs. 7, 8, 10, from the northern ones. The slit band is 

 placed a little above the middle line or exactly on it in the body whorl, near the 

 upper suture on the other whorls. As to its course it follows not always the same line^ 

 but deviates from it obliquely as seen in figure 7. It is much prominent, more so 

 than in any one of the preceding and nearly as much as in the following. Details of 

 it are given in figs. 14 — 17. The crescents are of a most peculiar shape, figs. 15 — 16, 

 being lamellae divided into two lobes through a large, oval slit widening backwards. 

 The two lobes are of unequal size, the lower one usually larger. The deep groove 

 in the midst between them is longitudinally as well as concentrically striated. These 

 lamella3 have grown longer in the same proportion as both the bordering edges have 

 changed and, as seen in the longitudinal section fig. 17, become elongated as thin 

 lamella, directed obliquely towards the aperture and thinning out near the outer 

 margin. The slit band thus attains to a large size and in some as much as five millim. 

 in a transverse line. See fig. 12. In fig. 14 there is an enlarged transverse section, 

 in which two pairs of the lobes have been cut through. 



The depressed variety has five whorls, sloping in an acute angle to the slit band. 

 The aperture is transversally ovate, broader than high. The surface is richly sculptured 

 by a great number of spiral lines, varying from three to ten or more, crossed by lines 

 parallel with the lines of growth. Beneath the slit band the spiral lines are more 

 numerous and close, forming with the transverse lines a fine trellis work of minute 

 meshes and points, nearly alike the surface of a fine polishing file, fig. 3, 13. The 

 umbilicus is either open as to show all whorls, fig. 6, or jjartially concealed through 

 the acute angle formed by the interior lip of the aperture, f 3. 



The elongated variety, figs. 7 — 12, from the northern localities of Gotland is 

 turbinate with longer spire and ventricose whorls. There is usually only one spiral 

 ridge above the slit band, seldom two, but much prominent. Beneath the slit band 

 there is a varying number from a single longitudinal line to quite as many as in the 



