180 G. LINDSTROM, ON THE SILURIAN GASTROPODA AND PTEROPODA OF GOTLAND. 



10. Cyclonema? tenuissimum n. 



PI. XVIII fig. 38. 



Shell globose with six whorls, the body whorl several times as large as the spire. 

 The ornamentation consists of narrow spiral lines, very tine and closely set, especially 

 on the umbilical side. The suture is partly filled up by the overlying Avhorls. The 

 aperture is transversally ovate and the lips thin. Tlie umbilicus is deep and funnel 

 shaped. H. 10 mill., br. 11 mill. 



There is only one specimen as yet found from the limestone of Follingbo. 



11. Cyclonema? giganteum n. 



There exist only some fragments of the nucleus, by which it can be concluded 

 that this shell was turbinate with much ventricose whorls, of which three are extant in 

 the same specimen. There are also impressions of fourteen moderately elevated longitu- 

 dinal keels, the interstices between which are finely and transversally striated. This 

 fossil which in its size so much surpasses the other Cyclonemata, as well as almost 

 all other Silurian shells, can only hesitatingly be referred to this genus with which it 

 else coincides as to the ornamentation of the surface. H. 86 mill., breadth of body 

 Avhorl 95 mill. It has been found in the shale beds near Wisby and in Lumraelund. 



12. Cyclonema perversum n. 



PI. XXI fig. 65—56. 



Shell sinistral, to judge by the only existing fragment of three ventricose whorls, 

 elongated or turreted, ornamented by numerous thread like, somewhat irregular and 

 unequal, longitudinal stria3. These are crossed, especially near the aperture by coarser, 

 elevated lines of growth and for the rest by narrow, impressed lines. The suture is 

 moderately deep, the aperture is elongate and angular, acuminate in its upper and in- 

 ferior corners and on the middle of the inner lip. The lips are thin and straight. 

 The umbilicus is visible as a narrow slit. Size of the fragment: height 16 millim., br. 

 12 mill. 



The single specimen has been found in the upper gray limestone beds of the 

 hill of Linde. 



Gen. TROCHONEMA Salter. 



1859 Salter Canad. Organ. Remains Dec. 1, 27. 



Shell turbinate, elongated, keeled, loitk loide and open umbilicus, surrounded by an 

 elevated keel. 



I have adopted this genus for a widely spread shell, which cannot aptly be uni- 

 ted with any of the previously known. Salter thinks that Inachus angulatus Hisin- 

 GER (Oriostoma angulatum) probably is an extreme form of this group, but I cannot 



