Match the name of the animal with one characteristic and the phylum or class to which it belongs.
Petromyzon - Ectoparasite - Cyclostomata
Limulus - Body covered by chitinuous exoskeleton - Pisces
Adamsia - Radially symmetrical - Porifera
Ichthyophis - Terrestrial - Reptilia

Ichthyophis is a genus of limbless amphibians. Limulus is a genus of horseshoe crab belonging to the phylum Arthropoda. Adamsia is a genus of sea anemones belonging to the phylum Cnidaria. Petromyzon or sea lamprey is an ectoparasite and they are the most primitive vertebrates alive today and are called cyclostomes which mean round mouths. So, the correct answer is option A.