Tridacna

[ trih-dak-nuh ]

/ trɪˈdæk nə /

noun

a genus of giant clams inhabiting reefs in the South Pacific, attaining a diameter of 4 feet (1.2 meters) or more, and weighing over 500 pounds (227 kg).

Origin of Tridacna

1770–80; < New Latin, noun use of feminine of Latin tridacnus requiring three bites < Greek trídaknos, equivalent to tri- tri- + dákn(ein) to bite + -os adj. suffix

Examples from the Web for tridacna

I did not know the name at the time, but I afterwards learned that it must have been a specimen of the Tridacna gigas.
In the Eastern Seas|W.H.G. Kingston
The Chama (Tridacna) gigas, when at its full age and development, is the largest shell known.
A Conchological Manual|George Brettingham Sowerby
Strictly speaking, the Singapore oyster is a gigantic species of Clam, (Tridacna).
The Castaways|Captain Mayne Reid
A few are fashioned out of the thick portion of the shell of Tridacna gigas.
The Solomon Islands and Their Natives|H. B. (Henry Brougham) Guppy

Those most prized are fashioned out of the thickest part of the shell of Tridacna gigas towards the hinge.
The Solomon Islands and Their Natives|H. B. (Henry Brougham) Guppy