Carapace length approximately twice the maximum height in both sexes. Fused zone relatively narrow, vestibula correspondingly broad; about ten anterior marginal pore canals. Distal process of male copulatory appendage rounded, subovate, with a small, pointed posterior projection (P. caudata 4 ).
The taxonomic confusion over P. caudata has been discussed by Horne,1986b, who re-examined material recorded as P. caudata in the Brady and Norman collections, recognising two new NW European species (P. britannica and P. norvegica) in addition to the true P. caudata.
S Norway, at least some of the previous records of this species from the British Isles can be re-assigned to P. britannica. Records from further afield are also questionable and need confirmation.