Mussel and Cockle. 97 
Mussels, so called from the Naiades, fabulous 
divinities of the streams and rivers. The shells of 
many of these, which are of considerable thickness, 
are lined with the most brilliant nacre, and in these, 
as might be expected, pearls are sometimes found. 
One species, abundant in some English rivers, called 
the Mya Margaritifera, or, as some say, Uno elon- 
gates, has long been celebrated for this valuable 
production. It was most likely with pearls from 
this mollusk that Julius Czesar adorned a breast- 
plate, which he dedicated to Venus, and hung up 
in her temple. The rivers Esk and Conway were 
formerly celebrated as British pearl fishing-grounds; 
a Conway pearl was presented by her chamberlain, 
Sir Richard Wynn, of Gwyder, to Catherine, Queen 
of Charles the Second; and in the royal crown of 
Britain this jewel is said still to occupy a place. Sir 
John Hawkins, the circumnavigator of the globe, 
held a patent for the pearl-fishery of the River It, 
in Cumberland. The rivers of Tyrone and Donegal, 
in Ireland, have, or had, their pearl-bearing Mus- 
sels; we read of one which weighed thirty-six 
carats (a carat is nearly four grains), but not being 
of perfect shape and colour, it was only valued at 
forty pounds. We also read of another purchased 
by Lady Glenlealy, for ten pounds, and found to 
