Brady, 1868b
Description:
Carapace medium to large, 0.7-0.85 mm long, elongate subrhomboidal with narrowly rounded or bluntly pointed extremities, compressed. Weak caudal process well above mid-height position. Fused zone narrow. Female slightly higher and larger than male.
Mandible coxa long. Second leg with a short, slender knee seta. Fourth podomere of third leg with a strongly spinose anterior margin. Male copulatory appendage with three distal processes: the anterior one bicuspate, somewhat hookshaped, the central one curved, proximally broad, distally narrow and acuminate, the posterior one broad, lamellar; basal capsule subtrapezoidal with a rounded anterodorsal corner (P. ensiforme 5 ). Living specimens white or pale brown.
Habitat:
A littoral and sublittoral species, found both on algae and on sandy sediments.
Remarks:
Horne & Whittaker (1985d) re-examined the remaining type material of P. ensiforme in the Brady and Norman collections, finding that two closely similar but distinct species were represented, either of which could fit Brady's original description and illustrations. They chose as a lectotype the form which corresponds to most subsequent authors' concepts of P. ensiforme. The other species, P. angliorum, has a broader fused zone than P. ensiforme, and the two can be easily separated on the basis of their male copulatory appendages.
Two Mediterranean species described by G. W. Müller (1894), namely P. angustum and P. simile, as well as P. obliquum Sars (1866) from Norway, are remarkably similar to the two British species discussed above; all five may be distinguished from each other by careful comparison of their carapace shape, fused zone and male copulatory appendages, but it is clear that they form a closely related group of species. P. fleetense is also similar to P. ensiforme in carapace outline, but differs in the shape of the fused zone which has a characteristic posteroventral embayment, and in details of the copulatory appendages.
Distribution:
British Isles, Norway and N France.