| n. pl. | 1. | (Zool.) A class of Vertebrata, lower than fishes, characterized by their purselike gill cavities, cartilaginous skeletons, absence of limbs, and a suckerlike mouth destitute of jaws. It includes the lampreys and hagfishes. See Cyclostoma, and Lamprey. Called also Marsipobranchiata, and Marsipobranchii. |