Page:An Introduction to the Study of Fishes.djvu/91



lowermost sub-class of fishes, which comprises one form only, the Lancelet (Branchiostoma [s. Amphioxus] lanceolatum, possesses the skeleton of the most primitive type.





The vertebral column is represented by a simple chorda dorsalis or notochord only, which extends from one extremity of the fish to the other, and, so far from being expanded into