Definition of "cyclostome"
Any of various primitive jawless fish of the class Cyclostomata, such as the lamprey or hagfish.
Quotations
Except the cyclostomes, as the lampreys and sphagobranchiæ, which are not real fishes, as I shall show elsewhere.
1811, André Marie Constant Duméril, “On the Sense of Smell in Fishes”, in Journal of Natural Philosophy, Chemistry, and the Arts, volume 29, page 344