1869.] THE MALLEUS AND THE INCUS OF THE MAMMALIA. 397 
mandible, to the anterior margin of the anterior cornu of the hyoid 
(Hy"), 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, H 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 
Fig. 4. 
The tympanie cavity and the adjacent parts laid open from behind, and the apo- 
neurotic 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.S¢. 
suprastapedial cartilage. 6. 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. The exoccipital is supposed to be broken 
away to show the fenestral end of the stapes. 
