HESPERORNIS, an extinct bird from the Mid-Cretaceous of Kansas. Hesperornis ("western bird") was a flightless, swim ming and diving bird, nearly 4 ft. in length; the bill was long and slender, with teeth set in a continuous groove, filling the lower mandible to the tip, but confined to the basal portion of the upper mandible. Of the wing, only the humerus remained. The legs were strong, directed outward at right angles to the body, and moving together like a pair of oars. (See ODONTOR NITHES ; ORNITHOLOGY.)