chondrostei

from The Century Dictionary.

• In Müller's system of classification (1845), an order of ganoid fishes, characterized by the skeleton being partly cartilaginous, partly bony, and the skin naked or provided with osseous bucklers.—
• In Cope's system of classification, a primary division of actinopterous fishes, with an entire series of basilar segments of the abdominal ventral fins, and with no branchiostegal rays and no pterotic bone: synonymous with Chondroganoidea.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) An order of fishes, including the sturgeons; -- so named because the skeleton is cartilaginous.