114 a. LINDSTRÖM, ON TlIE SILUKIAN GAHT]i01^O])A AND TTKROPODA OK GOTLAND. 



which Dr G. J. Hinde kindly has sent me a cast to compare. It lias often been 

 confounded with Plenrot. balteata Phillips which is a quite different s|)ecies, as I have 

 learnt also through a cast kindly sent from Dr Hinde. 



26. Pleurotomaria limata nom. nov. 



Pl. X fig. 2—17. 



Euomphalus carinahis 1839. Sowerey in Sil. Syst.. 616, pl. 6 f. 10. 



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



1847. MuRCHisoN Silurian Rocks of Sweden, Qu. .lourn. Geol. Soc LoiuL, 29, 49. 



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



1867. Salter Siluria 3:d Ed., 531, pl. 24 f. 11. 



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



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



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

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

 mentioned below, the låter, tigs. 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 sutnre 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 lamelte 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 

 lamellas 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 

 lamelte, 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 

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

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

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

 the acute angle formed by the interiör 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 



