1876.] 



Auditory Ossicles of the Mammalia. 



103 



uterine growth, and hence is far less stable than in animals where it is 

 held together, speaking roughly, by the manubrium. 



The manubrium is rather short, and forms with the neck an angle of 

 about 140°. It is broader at the base than in the Simiidae, and flattened 

 laterally ; still the sides are slightly convex. The extremity is slightly 

 recurved and spatulate, and the processus brevis is very well developed. 



The body of the incus in Homo is well developed and rather longer 

 than deep vertically ; the crura are very divergent, and the " processus 

 brevis," or posterior crus, very high in the natural position of the bone, 

 is stout and rather long; the long, slender "processus longus " is gently 

 curved, and bears a small os orbiculare or Sylvian apophysis rather firmly 

 seated on a not very thin pedicle. 



The stapes of man is noted for the great width of its aperture, 

 although there is no canal between its crura as in many lower animals. 

 The head is proportionally rather small, and the anterior of the two 

 slender crura is the straightest. The footplate is necessarily wide hori- 

 zontally, but rather narrow vertically ; its outline is reniform, the upper 

 border being convex or arched, the lower is slightly concave in the 

 middle. Its posterior extremity is blunter than the anterior, and it is 

 somewhat convex towards the vestibule. 



Comparing the ossicula of Homo with those of the Simiidae it appears : — 



1st. That the ear-bones of Homo, Troglodi/tes, and Simia closely 

 resemble one another. 



2ndly. The malleus of Hylohates has greater affinities to the above 

 genera than to the lower monkeys, but the incus and stapes are of a 

 lower type. 



3rdly. The ossicula of Troglodytes nir/er are altogether most like those 

 of Homo ; but in the form of the head and articular surface of the mal- 

 leus Simla most approaches Man. The malleus of the gorilla is less 

 human than the chimpanzee's, the outer segment of the articular sur- 

 face being wide, whilst its manubrium more resembles that of Simia : 

 but the incus and stapes of T. gorilla are very much like the same 

 ossicula in Homo. 



4thly. Taking the characters of these high animals into general con- 

 sideration, we must conclude that they tend far more towards Homo 

 than to the tailed Old- World monkeys. 



The ossicula of the Cercopithecid.^3 possess several prominent 

 characters, some of which are absent in certain genera ; and they are 

 most marked in Macacus. These peculiarities are principally : — in the 

 malleus great shortness and great constriction of the neck, and a manu- 

 brium forming a very wide angle with the rest of the bone, possessing 

 both a processus brevis and a processus muscularis, and well dilated at 

 the extremity ; in the incus a square or high and narrow body, and in 

 the stapes extremely straight crura ; this latter feature is constant. 



Semnopitliecus in its incus, and in the slight lateral compression of the 

 well- developed head of the malleus, approaches the Simiidce, but in the 



