Bryozoans and brachiopods, nearly equal in abundance, form about 60% of the allochems in local limestone. Crinoids form about 20% and trilobitesnearly 10% of the allochems. According to detailed ...

These included brachiopods, which lived in shells resembling those of clams or cockles, and animals with jointed, external skeletons known as arthropods—the ancestors of insects, spiders ...