30 LAND AND FRESH-WATER MOLLUSKS. 
times also fished to a great extent for the orna- 
mental excretions to which it is subject. The 
pearls from Mytilus edulis are very much in- 
ferior in quality and size to those from the 
Unio. Those of the Conway had great fame. 
Extensive fisheries existed in the rivers of 
Tyrone, Derry, Donegal, near Dundalk, near 
Waterford, and in Kerry. In Scotland, the Tay 
was the seat of a pearl fishery. “It is said,” 
writes Captain Brown, ‘that the pearls sent 
from thence to London from the year 1761 to 
1764 were worth £10,000, and it is not uncom- 
mon at the present day to find pearls in the 
Teith and Tay worth from £1 to £2 sterling 
each.” The var. Loissyi was formerly much 
sought for in the Black River, Kirk Braddam, 
Isle of Man, on account of its pearls. 
Anopon cyengeus—(the Swan Mussel) (Pl. L., 
fie. 1)—attains a size considerably larger than 
the Unios. The maximum size exceeds in length 
eight and in breadth four and a half inches. 
It is readily distinguished by its rather thin, 
oval (truncated behind) shell, compressed in 
the young, but becoming ventricose with age. 
The epidermis is glossy, dull green, more or less 
tinged with dusky, and slightly radiated; the 
inside of the shell is bluish-white, pearly in young 
and yellowish-white in old shells. The umbones 
