The term used for "marine lung" ("pleumōn thalattios") appears to refer to jellyfish of the type the ancients called sea-lung. The latter are mentioned by Aristotle in "On the Parts of Animals" as being free-floating and insensate. They are not further identifiable from what Aristotle says but some "pulmones" appear in Pliny as a class of insensate sea animal; specifically the "halipleumon" ("salt-water lung"). William Ogle, a major translator and annotator of Aristotle, attributes the name sea-lung to the lung-like expansion and contraction of the Medusae, a kind of Cnidaria, during locomotion. The ice resembled floating circles in the water. The modern English term for this phenomenon is pancake ice.