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Show 1869.] THE MALLEUS AND THE INCUS OF THE MAMMALIA. 397 mandible, to the anterior margin of the anterior cornu of the hyoid (Hy1), the upper part of which is entirely cartilaginous. The hyoidean cartilage ascends behind the quadrate bone, with a slight backward convexity, until it has nearly reached the skull, and then appears to be suddenly bent into the form of a little scroll with a backward concavity (fig. 3, E St). The upper end of the scroll becomes connected with the skull; the concavity is filled up by aponeurotic fibres. The aponeurotic expansion which has been mentioned covers the The tympanic cavity and the adjacent parts laid open from behind, and the aponeurotic expansion removed, in Sphenodon punctatum. Five times the size of nature. The letters as in fig. 3, except:-Pa. Parietal. Pc.C. Parotic cartilage. S.St. suprastapedial cartilage, b. Origin of this cartilage from the stapes, a. Foramen included between it and the extrastapedial. Mm. The cut edge of the mucous membrane. Tymp. The pharyngeal recess which takes the place of the tympanic cavity. Tbe exoccipital is supposed to be broken away to show the fenestra! end of the stapes. |