Some single-celled plankton have skeletal bodies, comprised in this case of calcium. This is a bottom living foraminiferan which can be the size of a penny. From the numerous pores in its surface stream conveyor belts of cellular cytoplasm returning organic material to the cell mass within the calcareous shell and rejecting non organic frass to the sea floor. Such animals occur in such numbers that across the eons of time they can form geological strata.
Lizard Island, Australia (1986)
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