563 



much importance, that tlie author was rewarded with a 

 munificent premium from the ftates of the kingdom on 

 that account. 



It is, however, fuppofed, that perforations, or par- 

 tial frattures in the fhell, will occafion the produftion of 

 pearls ; for as thefe produce diflortions, and ruggednefs 

 m the fhells, it appears to have the fame effeft as on 

 fuch as acquire it by age, and common accidents : but 

 how thefe (hells are opened without deftroying the ani- 

 mal, and xhe. pearl taken out, (which is faid will be re- 

 newed again after a certain period) we do not pretend 

 to determine. 



- Mya deprefTa. Don. Br. Shells, iii. t. 101. Ovalis, 



Mya ovata. Don. Br. Shells, iv, t. 122. p. 34, 



Although Mr. Donovan has given thefe two fiiells as 

 diltinft, he very juftly exprelfes a doubt. That they are 

 only varieties we cannot hefitate to determine ; and we 

 have already gone further, by giving them as ponderous 

 varieties of our Mya Ovalis. Donovan obferves, both 

 thefe fhells inhabit the New River, near London, and 

 the Froome in Somerfetjliire. We have found them 

 in the Avon, many miles above and below its conflux 

 with the Froome : at Bath they are thrown up in great 

 abundance after floods, and commonly ufed for putting 

 colours in. 



C c c c 2 That 



