Emerita. Emerita is a small genus of decapod crustaceans, known as mole crabs or sand crabs. These are small animals that burrow in the sand in the wash zone and use their antennae for filter feeding.merita is a small genus of decapod crustaceans, known as mole crabs or sand crabs. These are small animals that burrow in the sand in the wash zone and use their antennae for filter feeding.