[ 5 ] 
boring’ their cavities ; and they are found In moulds 
as exactly fitted to their bodies, as thofe are to melted 
matter caft into -them by a founder. It may, 
however, be fuppofed that the ftone and wood does 
actually give way to the growth ol the animal within, 
becaufe the fadfs are well attefted ; but how this comes 
to pafs,in thefe Pholades and cylindrical Mulcles, and 
by what means, toads, &c. can receive aliment 'to 
caufe their growth, without any external commu- 
nication, mufi: yet remain among thofe fecrets of 
nature, which we cannot but admire, without knowing 
how they are brought about. 
Explanation of 'the Table*. 
Fig. I. Is a view of the furface of one of the great 
valves, with the edges of the two longi- 
tudinal pieces, and with portions of the 
fmooth parts at the round extremity or 
bafe. 
II, Shews the anteriour edge of the Pholas co- 
vered by the long fmooth white piece, and, 
at the bafe, having part of the fmooth 
portions of the great valves in view. 
III. Reprefents the pofteriour edge of the Pholas, 
with the round white piece upon the bafe 
end, and the long ditto, which is larger 
than that of the fore edge, running to- 
wards the apex. 
IV. Is 
