Leptocardia

‖n. pl. [ NL., fr. Gr. lepto`s small + kardi`a the heart. ] (Zool.) The lowest class of Vertebrata, including only the Amphioxus. The heart is represented only by a simple pulsating vessel. The blood is colorless; the brain, renal organs, and limbs are wanting, and the backbone is represented only by a simple, unsegmented notochord. See Amphioxus. [ Written also Leptocardii. ] [ 1913 Webster ]