MACHAERIDIA – Description from Adrain, 1992
General Description: Marine animals with a metamerically arranged, calcitic exoskeleton, composed of either two or four longitudinal series of posteriorly imbricated sclerites; individual sclerites composed of two distinct calcite layer; outer layer formed by lamellar deposition, bearing fine growth lines and coarser rugae developed parallel to growth lines; inner layer formed by terminal addition of calcite elements in series radiating outward from sclerite umbo; all sclerites with an inner groove running anteriorly from the umbo on the inner surface; muscle scar universally present on inner surface. Historically, Machaeridans have been regarded as echinoderms or possibly descendents of echinoderm ancestors.
Plumulites sp. – possibly P. trentonensis Withers – Description from Ruedemann, 1942
Description: Has kiteshaped plates that are short and broad. The apical part of the plate is not attenuated with proximal angles that are widely and almost equally truncated.
