290 THE OLDEST AIR-BREATHERS 



been found in a thin, shaly layer, containing debris of plants 

 and crusts of Cyprids, and which was probably deposited at 

 the outlet of a small stream flowing through the coal-formation 

 forest. The two species found in Illinois occur, according to 

 Bradley, in an underclay or fossil soil which may have been 

 the bed of a pond or estuary, and subsequently became a 

 forest subsoil. The Erian .species occurs in shales charged 

 with remains of land plants, and which must consequently 

 have received abundant drainage from neighbouring land. It 

 is only in such deposits that remains of true land snails can be 

 expected to occur ; though, had fresh water or brackish water 

 Pulmonates abounded in the Carboniferous age, their remains 

 should have occurred in those bituminous and calcareo-bitu- 

 minous shales which contain such vast quantities of debris of 

 Cyprids, Lamellibranchs and fishes of the period, mixed with 

 fossil plants. 



The specimen first obtained in 1887 having been taken by 

 Sir Charles Lyell to the United States, and submitted to the 

 late Prof. Jeffries Wyman, the shell in question was recognised 

 by him and the late Dr. Gould, of Boston, as a land shell. It 

 was subsequently examined by M. Deshayes and Mr. Gwyn 

 Jeffries, who concurred in this determination ; and its micro- 

 scopic structure was described by the late Prof. Quekett, of 

 London, as similar to that of modern land shells. The single 

 specimen obtained on this occasion was somewhat crushed, 

 and did not show the aperture. Hence the hesitation as to 

 its nature, and the delay in naming it, though it was figured 

 and described in the paper above cited in 1852. Better 

 specimens showing the aperture were afterward obtained by 

 the writer, and it was named and described by him in his 

 " Air-breathers of the Coal Period," in 1863. Owen, in his 

 "Palaeontology," subsequently proposed the generic name 

 Dendropupa. This I have hesitated to accept, as expressing 

 a generic distinction not warranted by the facts ; but should 



