1) Family pholadidae 2) Mollusk family 
Pholadidae, known as piddocks or angelwings, are a family of bivalve mollusc similar to a clam; however, they are unique in that each side of their shells is divided into 2 or 3 separate sections. Furthermore, one of the piddock`s shells has a set of ridges or `teeth`, which they use to grind away at clay or soft rock and create tubular burrows......
[n] - a family of Bivalvia
family Pholadidae noun a family of Bivalvia