294 THE OLDEST AIR-BREATHERS 



in those succulent and nutritious leaves and fruits which are 

 most congenial to land snails. It is to be observed, however, 

 that we know little as yet of the upland life of the Erian or 

 Carboniferous. The animal life of the drier parts of the low 

 country is indeed as yet very little known ; and but for the 

 revelations in this respect of the erect trees in one bed in the 

 coal formation of Nova Scotia, our knowledge of the land 

 snails and Millipedes, and also of an eminently terrestrial group 

 of reptiles, the Microsauria, would have been much more 

 imperfect than it is. We may hope for still further revelations 

 of this kind, and in the meantime it would be premature to 

 speculate as to the affinities of our little group of land snails 

 with animals either their contemporaries or belonging to 

 earlier or later formations, except to note the fact of the little 

 change of form or structure in this type of life in that vast 

 interval of time which separates the Erian period from the 

 present day. 



It may be proper to mention here the alleged Pulmonifera 

 of the genus Palxorbis described by some German naturalists. 

 These I believe to be worm tubes of the genus Spirorbis, and 

 in fact to be nothing else than the common S. carbonarius or 

 S. pusillus of the coal formation. The history of this error 

 may be stated thus. The eminent palaeobotanists Germar, 

 Gceppert and Geinitz have referred the Spirorbis, so common 

 in the Coal measures to the fungi, under the name Gyromyces, 

 and in this they have been followed by other naturalists, 

 though as long ago as 1868 I had shown that this little 

 organism is not only a calcareous shell, attached by one side 

 to vegetable matters and shells of mollusks, but that it has the 

 microscopic structure characteristic of modern shells of this 

 type. 1 More recently Van Beneden, Csenius, and Goldenberg, 

 perceiving that the fossil is really a calcareous shell, but 



1 "Acadian Geology," 2nd edition, p. 205. 



