The geouck (pronounced /ˈguːiːdʌk/ "gooey duck"), Panopea abrupta, is a species of large saltwater clam, a marine bivalve mollusk. The shell of this clam is large, about 15 to over 20 cm in length (about 7 to 9 inches), but the long siphons make the clam itself much longer; the "neck" or siphons alone can be one meter in length.