English: The holotype of H. quadriformis reconstructed by analogy with modern stauromedusae, showing the paired arms at each corner of the calyx tipped with hypothetical secondary tentacles and shorter divided primary tentacles at the margin of the calyx with hypothetical adhesive pads inferred from the morphology of modern stauromedusae. Approximate scale bar 5 cm. (A) is an oral view and (B) is the lateral view of the calyx and peduncle © Bob Nicholls.