The Madison Cave isopod is an eyeless, unpigmented, freshwater crustacean. It belongs to a family that consists of mostly marine species and a small number of freshwater species. The species is the only member of its genus and is the only freshwater cirolanid isopod north of Texas. Its body is flattened and bears seven pairs of long walking legs. The first pair of legs are modified as grasping structures. It has a pair of short antennae and a pair of long antennae. Males reach a length of 0.6 inches; females reach a length of 0.7 inches. While most cave isopods spend the majority of their time walking along the bottoms of streams and pools, Antrolana lira spends much of its time swimming freely through flooded caves formed in ancient limestone.