1876.] 



Auditory Ossicles of the Mammalia. 



107 



markable for the strong resemblance \a hicb the ossicula of the adults of 

 the smaller species bear to those of the mature foetus or 3"oung of the 

 larger members of those families. The head of the malleus is ahvajs 

 ill-developed, the processus muscularis always present, and the manu- 

 brium is frequently very long. In the adult Bos the great shallowness 

 of the articular facet of the malleus, the bold curve of the manubrium, 

 the very high and well-developed body of the incus with its long and 

 divergent processus brevis, and the quadrilateral form of the stapes are 

 all very distinctive ; on the other hand, in the adult Ouis the articular 

 surface is deeper and the facets less level than in Bos, and the manu- 

 brium is almost straight ; nor is the body of the incus so developed, 

 although the posterior crus is very long. The stapes is nearly as qua- 

 drilateral in a large adult Ovis aries as in Bos, but it often remains 

 triangular in small sheep. 



In the lamb or fully developed foetal sheep the articular surface of the 

 malleus is still deeper cut and the facets more prominent than in the 

 adult ; the incus has a sliallow body and the stapes is quite triangular. 

 -Most of the remaining Bovidae imitate, in the ossicula of the adults, the 

 types of the ox, the sheep, or the lamb. Thus in the wild sheep, the 

 goats, and many small antelopes, as Xemorhoedus, Oreotragus, and Saiga, 

 the ossicula much resemble those of the young Ovis aries ; Gazella and 

 its allies are more bovine in the type of the malleus, whilst the stapes is 

 generally triangular, even in the adult : the incus appears quite transi- 

 tional between Ovis and Bos, the body being almost square ; indeed as 

 the posterior crus is sometimes rather short in these antelopes, that 

 ossicle approaches the pig and chevrotain type. Nanotragn.s, Cepludo- 

 l^hus, Keotragus, Tetraceros, and Xanolioedus are also balanced in characters 

 between Bos and Ovis. 



Kohus, Tragelaphiis, AlcelapJnis, and Catohleixis lean more, in the 

 general characters of the auditory ossicles, towards Bos ; the gnus are 

 remarliable for the great length of the manubrium, which is straighter 

 than in the ox. In the adult Ovihos and Anoa the ossicula are slightly 

 more calf-like than ox-like. 



The ossicula of Camelopardalis are remarkably like those of Bos, and 

 undergo similar changes during the growth of the animal. In Antilocapra 

 the ossicula have not strongly defined characters, although perhaps they 

 most resemble those of the medium-sized antelopes. The quadrilateral 

 form of stapes allies it to Ovis ovBos; the incus, as in Gazella, may either 

 be considered intermediate between the form in those t^^ o domesticated 

 ruminants, or (as the posterior crus is not long) to relate the prong-horn 

 antelope to the Chevrotains. 



In the Cervidce the malleus always retains in the adult the characters 

 seen in the fully developed foetal ox, the articular surface having well- 

 marked facets, and the manubrium being almost straight. The processus 

 muscularis is large in the genus Cervit.s. The bcdy of the incus is always 



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