The Sea Lamprey

The first family in the catalogue, Petromyzonidae, is, appropriately, the most ancient. It belongs to the class Marsipobranchii, which includes both lampreys and hagfish, and which is introduced by Wheeler as follows: ‘This small group of slimy-skinned eel-like creatures are the most primitive of all living vertebrates. They are not, strictly speaking, fish, but as they are fish-like in appearance and edible, they are thought of as fishes ...