THE OLDEST AIR-BREATHERS 29 1 



the shell be considered to require a generic or sub-generic 

 distinction, Owen's name should be adopted for it. There 

 seems, however, nothing to prevent it from being placed in 

 one of the modern sub-genera of simple-lipped Pupae. With 

 regard to the form of its aperture, I may explain that some 

 currency has been given to an incorrect representation of it, 

 through defective specimens. In the case of delicate shells 

 like this, imbedded in a hard matrix, it is of course difficult 

 to work out the aperture perfectly ; and in my published 

 figure in the "Air-breathers," I had to restore somewhat the 

 broken specimens in my possession. This restoration, speci- 

 mens subsequently found have shown to be very exact. 



As already stated, this shell seems closely allied to some 

 modern Pupae. Perhaps the modern species which approaches 

 most nearly to it in form, markings and size, is Macrocheilus 

 Gossei from the West Indies, specimens of which were sent to 

 me some years ago by Mr. Bland, of New York, with the 

 remark that they must be very near to my Carboniferous 

 species. Such edentulous species as Pupa [Leucochila) fallax 

 of Eastern America very closely resemble it ; and it was re- 

 garded by the late Dr. Carpenter as probably a near ally of 

 those species which are placed by some European concholo- 

 gists in the genus Pupilla. 



Pupa vetusta has been found at three distinct levels in the 

 coal formation of the South Joggins. The lowest is the shale 

 above referred to. The next, 1,217 feet higher, is that of the 

 original discovery. The third, 800 feet higher, is in an erect 

 Sigillaria holding no other remains. Thus, this shell has lived 

 in the locahty at least during the accumulation of 2,000 feet 

 of beds, including a number of coals and erect forests, as well 

 as beds of bituminous shales and calcareo-bituminous shale, 

 the growth of which must have been very slow. 



In the lowest of these three horizons the shells are found, 

 as already stated, in a thin bed of concretionary clay of dark 

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