The Arcoida is an extant order of bivalve molluscs. This order dates back to the lower Ordovician period. They are distinguished from related groups, such as the mussels, by having a straight hinge to the shells, and the adductor muscles being of equal size. The duplivincular ligament, taxodont dentition, and a shell microstructure consisting of t...
Found on
http://en.wikipedia.org/wiki/Arcoida
(from the article `bivalve`) ...demibranchs of weakly united filaments; mostly marine; some cemented; most epibyssate; some infaunal; representative of the earliest ...
Found on
http://www.britannica.com/eb/a-z/a/96
No exact match found.
