Arthroacantha carpenteri   CLASS - Crinoidea ORDER - Monobathrida FAMILY - Hexacrinitidae GENUS/SPECIES - Arthroacantha carpenteri ROCK UNIT - Arkona Shale AGE - Devonian (380 million years old) LOCALITY - Arkona, Ontario, Canada A waste-eating snail (platycerid) is still attached to the anal opening of this crinoid crown (main body portion). These snails appear to mimic the exterior surface of the different crinoids they attach to. For example, spiny crinoids commonly possess spiny snails. PRI 42102