OF THE MAMMALIAN OSSICULA AUDITUS. 379 



In Hylobates (PL LVIII. fig. 6) the malleus (which is rather small even in a large 

 Gibbon's skull) resembles in many respects that of the Chimpanzee. The upper part 

 of the head projects forwards ; its articular surface is very wide externally, after the 

 Troglodytes type. Prom the fore part of the head projects a thin fringe of bone, which 

 does not join the root of the processus gracilis as in the Cynomorpba, and is repre- 

 sented, as in this genus, in some mallei from new-born children. The neck is short 

 and constricted ; the manubrium is as short as in Man, and much curved ; it has a very 

 prominent, outwardly directed processus brevis, and a distinctly spatulate dilatation at 

 the tips ; the whole angle forms, with the neck, an angle about as wide as in Homo, not 

 being so obtuse as in the Cercopithecidse. Moreover the neck, though short and con- 

 stricted, is longer than in Semnopithecus, which has the most distinctly necked malleus 

 of all the next group. Altogether the affinities of the malleus of a Gibbon tend more 

 towards Homo than to the tailed monkeys. 



In H. syndactyla and H. leucisciis (and probably in other Gibbons, only not con- 

 stantly) a distinct "processus muscularis " for the attachment of the tensor tympani 

 exists. In the latter it is seen as a distinct projection from the inner edge of the manu- 

 brium, at some distance from its root. In H. syndactyla it is reduced to a very small 

 tubercle on the root, almost on the site of the attachment of the tendon in Homo. 



The iucus in the Siamang (H. syndactyla) has a body of the same form as in Homo ; 

 in a specimen of that ossicle from H leuciscics the body is higher and narrower, whilst 

 in an incus from another Hylobates the body is as narrow as in some of the Cebidse. 



The stapes of Hylobates has always curved, divergent crura, and a wide aperture *'. 

 This is particularly marked in H. syndactyla. In this ossicle the Gibbons are allied to 

 Homo, Simla, and Troglodytes, in a manner not nearly so apparent in the malleus, and 

 still less in the incus. The very straight and not very divergent crura of the stapes in 

 all the tailed monkeys, even Semnopitliecus, distinguish that group of the Quadrumana 

 not less from Hylobates than from Homo t- With regard to the ossicula of the Simiidse, 

 in general, it may be briefly stated, in conclusion : — 



I. That the ossicula of Troglodytes niger are, taken as a whole, most like those of 

 Homo. T. gorilla closely resembles Homo in its incus and stapes, but less in its malleus ; 

 Simia more resembles Homo in the head and articular surface of the malleus. 



II. Though the incus of some species of Hylobates exhibits a tendency to low type, in 

 the malleus, and particularly in the stapes, this genus is quite anthropoid. 



III. In their ossicula, but most markedly in the stapes, these apes are much more allies 

 to Homo than to the lower monkeys. 



* In the Hylobates of uncertain species just referred to, the stapes hore on its foot-plate a distinct umbo, or central 

 convexity on the vestibular aspect. 



t From want of a sufficient number of good specimens when I contributed the communication already quoted to 

 the Eoyal Society, I was under the impression that the Gibbon's stapes was of a low type ; but I am now, after 

 more favourable opportunities, compelled to modify that assertion. 



