This image shows an aquatic isopod.  Although many members of this order are aquatic, some (such as pill bugs, sow bugs and wood lice) are among the few terrestrial crustaceans. They are, however, restricted to moist places such as under rocks, logs, leaf litter, etc.  because of their gills.  Isopods have bodies that are flattened dorsoventrally and lack a carapace.