Elphidium is a genus of foraminifera

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

n protozoa, one of the more common genera found near coasts. Like other forams, fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s from different species are used to date rocks.

Elphidium shows dimorphism with alternating generations.
The complete cycle for Elphidium crispum takes two years in the shallower marine regions, although it may be delayed at deeper stations.
Asexual reproduction reaches a peak in spring of first year.
Sexual reproduction begins early in the second spring as temperatures begin to rise.
The gametes conjugate outside in open sea to produce zygotes and the B form then develops and matures during the second summer.