[2] Fossils of Modiolus capax have been found in Miocene epoch deposits, suggesting that this species is between 5.3 and 20.4 million years old.

The external surface of the shell is blue to bright orange brown, while the inside is reddish-violet on the posterior half.

[7] This species is present in Santa Cruz, California, to Playa, Peru and in Galapagos Islands.

They live on rocks, boulders, and pebbles on the sea bottom and attached to wood pilings.

The reproduce by broadcast spawning, by releasing gametes into the sea where fertilization takes place.