Burrow - Ophiomorpha

Ophiomorpha is a classification of trace fossils believed thought to be the pellet-lined burrows of crustaceans. This is based on observations of modern day ghost shrimp and some crab species that are known to line their burrows in a similar manner when sediments are soft.  The pellets can have a fecal origin or can be sand/silt cemented with oral secretions (think spit balls).