This Ordovician limetones cobble is approximately
15 centimeters in length. Along with the crinoid holdfasts (which
look like small volcanoes) can be seen small, dark holes. These
are "worm" borings known as Trypanites. The
cobble probably formed from an infilling of a burrow, giving
it a somewhat sinuous shape. It was cemented and then exhumed
on the seafloor. (See a diagram of Trypanites.)
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