Complex sentence: Variety "polychaeta" appears to be relatively rare and it may have been extirpated from the type locality--around Mud Bay near Olympia, Washington--as a result of urban expansion.
Split into simpler sentences: Variety "polychaeta" appears to be relatively rare. It may have been extirpated from the type locality--around Mud Bay near Olympia, Washington--as a result of urban expansion.