OF THE MAMMALIAN OSSICULA AUDITUS. 425 



brium has a well-bordered outer aspect of almost equal breadth throughout ; there is a 

 sharp angular projection at its base; and it is but slightly recurved and very little 

 dilated at the tip. 



The incus is high and narrow ; its articular surface is deeply cut ; and when there is a 

 tailed prolongation of the lower facet on the malleus, a corresponding peculiarity is seen 

 on that facet on this bone. Both crura are very short ; the lower is very divergent and 

 boldly curved. The stapes is almost quadrilateral ; the head is very broad, with a pro- 

 minent process for the stapedius tendon ; the crura are stout and almost parallel ; the 

 anterior, which is the thinnest, is inserted into the extremity of the base, which is rather 

 thin and almost plane. 



In general characters the ossicula of Antilocapra closely resemble those of the Bovidse. 

 The body of. the incus is almost as stout and square as in the Pigs and Trayidus; but 

 this feature is seen in Gazella. 



The Bovnxa:. 



In this family it is hard to find distinctive features in the auditory ossicles of different 

 species, while, to add to the difficulty, in many instances these bones undergo considerable 

 changes during the growth of the animal ; so that little reliance can be placed on any 

 conclusions based on the observation of one specimen alone from any species. It is 

 necessary to examine duplicates as well as examples from different species of the 

 same genus. Through the kindness of Sir Victor Brooke, Bart., the author has been 

 enabled to collect a large series of the ear-bones of this order from the skulls in that 

 gentleman's fine collection of skeletons of Ruminants. 



Beginning with the Common Sheep (Ovis aries), it is highly important to select 

 complete series of the ossicula from individuals of all ages, for reasons immediately to 

 be explained. 



Taking a set from the skull of an adult sheep (PL LXI. fig. 16), the malleus will 

 be seen to have the upper and anterior part of its head ill developed, as in Antilocapra, 

 and unlike Sus and its allies. The articular surface (a most important region to observe 

 closely) is wide vertically as well as laterally, and also deeply cut ; each facet is dis- 

 tinctly saddle-shaped, with a sharp vertical ridge down the middle. The neck is cylin- 

 drical and sharply curved, as in most mallei of this type ; the lamina is of moderate 

 breadth. The processus muscularis is curved and prominent, but not very long. The 

 manubrium is long and slender, compressed laterally, but not broad even at the base, 

 on the outer extremity of which is a rectangular projection, hardly to be called a pro- 

 cessus brevis. The outer aspect is sharply bordered and extremely narrow, hardly dilating 

 at the extremity, which is but little recurved. 



From repeated observations, I find that the malleus of an adult domestic Ovis closely 

 resembles that of a foetal Bos taurus of about the sixth week (PL LXI. fig. 15) ; but at 

 birth the characteristic, extremely shallow articular surface, and strongly curved manu- 

 brium, are always found in the ox ; the outer aspect of that process, too, is very broad 

 in foetal calves, though never in adult sheep. The same articular surface is very deeply 

 cut in the mallei of lambs. 



