P. walteri, an eyeless species of tiny size and thin body, shows numerous original characters. By its general morphology, it is one form of Asellid best adapted to the phreatic waters where it exists in large settlements. It is also able to live in the psammic biotope in a manner similar to Microparasellids. The females lay only 6 to 10 normal sized eggs. There is no indication of oostegits outside the breeding period. In some populations, the small number of eggs, correlated with the small size, seems to be compensated by a sex-ratio favorable so the females.