 Chilton originally thought this specimen was a male, but later realised that it was in fact female.Other specimens have been collected near sea level, but have not been described in the literature.When he realised that he had mis-sexed his Mount Anglem specimen of "P. propinquus", Chilton also realised that the material he had described under that name from Rona Bay, Wellington, was a third species, which he named "P. helmsii" in 1918.