The freshwater crabs of the Barbilla National Park, Costa Rica (Crustacea : Brachyura : Pseudothellphusidae), with notes on the evolution of structures for spermatophore retention

The Barbilla National Park, a natural area of high biodiversity on the Cari bbean slope of Costa Rica, possesses two species of freshwater crabs that s hare the same biotope in different localities of the Park. The first specie s, Potamocarcinus magnus (Rathbun, 1896), one of the largest species of the family Pseudothelphusidae, is widely distributed in Middle America, from C osta Rica to Southern Mexico. The other species is a new species, Ptychopha llus barbillaensis. This is a species of small crabs, possibly restricted t o the National Park and neighboring areas. It can be distinguished from all other species in the genus by the form of the receptacle formed in the ape x of the male gonopod, possibly for the retention of spermatophora during c opulation. The species of Ptychophallus Smalley, can be arranged in a morph ocline according to the relative development of this receptacle, with the p resent new species midway between the ancestral condition and the closed ch annel found in P. goldmanni Pretzmann, 1965.