THE 



CANADIAN NATURALIST 



AND 



(jfiuutaty ^ouvnal of ^dcucf. 



REVISION OF THE LAND SNAILS OF THE PALEO- 

 ZOIC ERA, WITH DESCRIPTIONS OF NEW 

 SPECIES. 



By J. W. Dawson, LL.D., F.KS. 

 (^From the American Journal of Science.') 



The Gasteropods as a class occur as early as the Upper Cam- 

 brian, but all the earlier known types are marine. That por- 

 tion of the group distinguished by the possession of air sacs 

 instead of gills (Pulmonifera) has not hitherto been found in 

 any formation older than the Carboniferous, aud only four Car- 

 boniferous species have been described. In the present paper I 

 propose to state some additional facts respecting the species 

 already known, to discuss their affinities, and to describe two 

 additional species, making six in all from the Paleozoic rocks, 

 including one from the Erian or Devonian. For reasons to be 

 mentioned in the sequel, I do not admit the genus Palcwrhis 

 founded, by some German naturalists, on fossils which I believe 

 to be tubes of Annelids. 



It may be useful to premise that of the two leading sub- 

 divisions of the group of Pulmonifera, the Operculate and In- 

 operculate, the first has been traced no farther back than the 

 Eocene. The second, or Inoperculate division, includes some 

 genera that are aquatic and some that are terrestrial. Of ihe 

 aquatic genera no representatives are known in formations 

 older than the Wealden and Purbeck, and these only in Europe. 

 The terrestrial group or the family of the Helicidce, which, 

 singularly enough, is that which diverges farthest from the 

 Vol. IX. cc No. 8. 



