unio. 149 



gle opposing tooth of the right valve is broad, erect, a 

 little twisted, somewhat arched, and deeply grooved at its 

 apex. 



Specimens are recorded to have reached the length of 

 five and a half inches, and the breadth of two and a half 

 inches ; the majority of individuals do not measure above 

 four and a half inches long and scarcely two broad. 



The animal of this species has a white-margined mantle 

 and foot. Troschel describes the lips as being broader than 

 long, and united for two-thirds of their length. The outer 

 branchial leaflets are free posteriorly, and lie in a fold of 

 the mantle ; the inner ones are partially united with the 

 foot. 



The Pearl Mussel, as this mollusk is familiarly called, 

 enjoys a distinguished reputation as one of the few in- 

 digenous bivalves which yield the beautiful productions 

 whose name it bears. In ancient times Britain enjoyed 

 some celebrity for its pearls, and they constituted one of its 

 attractions for Julius Csesar;* who, however, does not seem 

 to have reaped a very rich harvest, so far as quality went, 

 though he obtained enough in quantity to cover with them 

 a buckler, which he dedicated to Venus Genetrix, and sus- 

 pended in her temple. -J- The pearls used for the construc- 

 tion of his present were probably such as Roman ladies 

 would have scorned to wear, although they were osten- 

 tatiously offered to the goddess of beauty, for Pliny, who 

 narrates the circumstance, states at the same time that the 

 pearls from Britain were small and lustreless, and not to be 

 compared with those from the East. Tacitus, in his life of 

 Agricola, describes the pearls of Britain as " subfusca ac 

 I'wentia^ and among ancient Christian writers they are 

 mentioned by Origen and Bede. Pennant, and other 



■ Suetonius. t Pliny, ix. ch. XXXV. 



