SECTION Vllt- 163 



The fiphnnculus, or pipe of communU 

 cation from chamber to chamber in the 

 Ammonia, feems to be placed on the back 

 of the fpires, and not near the edges or in 

 the center of them ; but, as I can only 

 draw this concluiion from foffil ones, which 

 are very rarely fo perfe£l as to fhew the 

 pipe diftindly, we mull: yet remain un- 

 certain in regard to this and fome others 

 of their particular charadlers. 



It is a matter of aftonifhment in tliis 

 and other families of teftacea, that in ge- 

 neral the moft common foffil Shells are 

 the fcarcefl in the recent ftate, and vice 

 verfa. It could be readily explained, were 

 all the foffil kinds, not known recent, 

 reckoned Pelagian Shells, as the Amtno- 

 Ilia certainly are: but then what reafon 

 can be given for the Limpets, Sea Ears, 

 Volutes, Cowries, &c, which, though iti 

 extreme plenty recent, are very rarely 



M z found 



