Comparison and shared features of (a,b) the periotics and (c,d) the bullae of (a,c) C. marginata and (b,d) H. transatlanticus in ventromedial and posterolateral views, respectively. (a) Museum Victoria, Melbourne, Australia, C28531; (c) Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand, MM002119; (b,d) United States National Museum of Natural History, Washington DC, USA, 182962.