Invertebrates Here is the list of animal groups that will be treated in the section Invertebrates. ARACHNIDS, CENTIPEDES </br>AND MILLIPEDES INSECTS </br> AND RELATIVES POLYPS </br>AND RELATIVES CRUSTACEANS AND</br>HORSESHOE CRABS MOLLUSKS, LEECHES </br>AND WORMS ECHINODERMS, SPONGES</br>AND HYDROZOAS Back to “Animal Species” page