20 UNIONIDA. 
Britain by the reports of pearls found there, and Pliny 
states that he covered a buckler with them, which he 
dedicated to Venus Genetrix. 
Forbes and Hanley think that “ Cesar’s buckler 
was more probably covered with the pearls from 
Mytilus edulis” (the common sea mussel). This, how- 
ever, is not likely, as the pearls from this shell are 
exceedingly few and poor. Tacitus writes that they 
were of marine origin. 
Pennant states that as many as sixteen pearls have 
been found in a single Unio, and he gives an account 
of pearls of value having been found in Donegal and 
in the Conway. 
The ancient writers agree in disparaging the British 
pearls, justly considering those from the East finer in 
size and quality. 
Tacitus mentions a theory current in his time that 
the dull reddish colour of our pearls was due to their 
being collected from cast-up shells mstead of being 
gathered from living shells from the bottom of the sea; 
but he adds, with characteristic dry humour, that the 
fault probably lay in the pearls themselves, as other- 
wise his avaricious countrymen would have been sure 
to discover the best method of obtaiing them. 
Var. I. stnwata. Broader than the type, yellowish ; 
lower margin incurved. 
