178 G. LINDSTRÖM, ON THE SILURIAN GASTROPODA AND PTEROPODA OF GOTLAND. 



6. Cyclonema zonatum n. 



Pl. XVIII fis. 43—44. 



Shell small, turbinate, with obtusely elevated spire of six whorls. These are 

 evenly rounded, the body whorl of the satne size as the spire. The keels are longi- 

 tudinal, rounded, with interstices of equal size. The keel which is situated a little 

 below the median line of the body whorl is larger than the others and more distan- 

 tiated from the nearest and there thus originates a zone or a belt around the whorl. 

 Microscopically minute, transverse lines are crowded on the keels, deviating only slightly 

 from a vertical direction. Near the suture the longitudinal lines also are larger and 

 they leave a smooth zone between them and the suture. The aperture is obovate and 

 the umbilicus is narrow. H. 15 mm., br. 14 mill. 



Four specimens derived from the red limestone of the hill of Sandarfve. There 

 is also from the same locality a very large specimen (h. 18 mm., br. 18 mm.) which 

 perhaps belongs to this species. The longitudinal keels, however, are, below the middle 

 of the whorl, not so distinct, nor is the zone so definite. A shorter variety with 

 larger striai has been obtained from the shale beds north of Skäret in Fröjel. 



7. Cyclonema adstrictum n. 



Pl. XV fig. 49. 



Shell turbinate, of three whorls. The body whorl more than double the size 

 of all the others. It is nearly of elliptical outline, suddenly constricted in a more 

 narrow neck just above the suture; the next whorl is conically rounded without any 

 constriction. The surface is smooth and only through the magnifying lens a fine lon- 

 gitudinal striation is revealed, as of engraved lines, crossed by irregular short, arched 

 lines. The aperture is obovate with thin lips. There is no umbilicus. H. 15 mm., 

 br. 16 mm. 



Some specimens have been found in the red limestone of the hill of Sandarfve. This 

 is possibly identical with Naticopsis concinna Mac Coy Sil. Foss. Ireland p. 13, pl. I 

 f. 10. 



8. Cyclonema carinatnm Sowerby, 



PI. XVIII fig. 28—30. 



Turbo carinatus 1837. Sow. Sil. Syst., tnb. 5 f. 28. 



1843. Morris Catal. Brit. Foss. 165. 



1848. Bronn Nomencl., 1358. 



1850. D'Orb. Prodr. I, .30. 



1854. Morris Brit. Poss., 283. 



1855. Mac Coy Pateoz. Foss., 305. 

 Cyclonema octavia 1859. Salter ap. Siluria ed. 3, 548, pl. 24 f. 4. 



1873. Id. Cat. Cambr. Foss., 156, 172, 185. 



Turbo octavia 



Litorina octavia 



