OF THE MAMMALIAN OSSICULA AUDITUS. 423 



lateral type frequent in the Ruminants, the head being very broad ; the crura, wide apart 

 at their origin, are slender, and diverge little towards the base ; the aperture is large, 

 and almost circular. The base is stout, with a very convex umbo towards the vestibule, 

 as Hyrtl has previously observed. 



In the genus Sus all the above characters are strongly marked ; the lamina, however, 

 is much encroached upon even in a foetal pig. In Babirnssa alfurus the articular surface 

 of the malleus has but a faint line between the facets, the lower of which is considerably 

 narrower than the upper. This approaches the type of JPhacochcerus. The processus 

 muscularis is very long and stout ; the end of the manubrium is slightly but distinctly 

 recurved. 



In the Peccary (Dicotyles tajaqu, PI. LXI. fig. 7) the malleus has a longer and a 

 thinner neck than in Sus, much less abruptly curved, and a wide, perfectly papery lamina 

 between it and the processus longus ; the manubrium, which forms a more obtuse angle 

 with the neck than in the other pigs, has a rather wider outer surface, and a distinctly 

 broader and more spatulate extremity. 



The more compact and less laminar expanse of bone between the neck and the pro- 

 cessus gracilis in the Pig, as compared with the Peccary, might be explained by its 

 greater size ; and, indeed, in the larger animal in any Order there is often a tendency 

 to such thickening of that area ; still, in the large malleus of the Lion this lamina is 

 as thin, in comparison with the rest of the bone, as the corresponding structure in the 

 Cat and Genet ; on the other hand, it is denser in the Hyaena, which is intermediate 

 in size between them. Hence the degrees of density of the lamina constitute fair 

 generic distinctions. 



The incus of Dicotyles is even higher and narrower than in Sus; the processus longus 

 is rather longer. The stapes has a broad head, very straight crura, and a very thick 

 base, with an umbo convex towards the vestibule, as in Sus. 



In the Chevrotains, Trag.uliDtE (PL LXI. fig. 8), the head of the malleus is small; 

 and the articular surface is deeply cut, with a sharp groove between the facets, which are 

 both saddle-shaped, a sharp convex ridge running vertically down their surfaces, near the 

 outer margin, as in the Pigs, whilst in most of the Bovidaa the facets are nearly plane. 

 The lower facet is almost as wide as the upper. The neck is shorter than in Sus, and con- 

 sequently much shorter than in most Ruminants ; but the malleus resembles that of the 

 latter group of Artiodactyla in the bluntness of the angle at the outer side of the base of 

 the manubrium, which, moreover, forms a very obtuse angle with the neck ; the processus 

 muscularis is short, but stout. The incus invariably retains the solid square form seen 

 in the Pigs ; and the crura are as short. The stapes has a small head and more divergent 

 crura than in Sus ; the base is very thick and quite plane ; the crura are both inserted a 

 perceptible distance from its extremities. Hence this bone, with its divergent limbs, 

 has the form of an almost equilateral triangle, as seen in some Antelopes, particularly in 

 Gazella, differing from the almost quadrilateral stapedes of both Bos and Sus. The 

 corresponding ossicle in the Cervidse, having a narrow base, with straight, equal crura, 

 is intermediate in form. 



In Tragulus javanicus the manubrium does not form quite so obtuse an angle with 



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