OF THE MAMMALIAN OSSICULA AUDITUS. 473 



In every respect this stapes approaches the type of the higher Mammalia, as does that 

 ossicle in the Ant-eaters and Orycteropus, contrasting strongly with the Sauropsidan 

 stapes of Manis and the tendencies in that direction already described in the Sloths. 



In Dasypus villosus and D. minutus the ossicula are almost identical with the same in 

 D. sexcinctus. The stapes in the Hairy Armadillo is even more slender than in the six- 

 banded species ; the processus muscularis is more prominent in the malleus of D . minutus 

 than in the larger species. 



In the Peba Armadillo (Tatusia peba, PL LXIV. fig. 3), the ossicula resemble greatly 

 those of Dasypus. The processus muscularis mallei is obsolete in the College specimens ; 

 the crura of the incus are of similar character ; the stapes is of slender form with a wide 

 aperture. I have not found the head of this ossicle to be unossified in any young or 

 adult Tatusia, as Hyrtl asserts of T. hybrida; but that portion is readily broken 

 off from the fragile crura. The malleus in the new-born Tatusia (fig. 7) has an ill- 

 developed head and a similar manubrium to that of Priodon (fig. 5). It is remarkable 

 that whilst the malleus of the adult Tatusia or Dasypus resembles that of Equus, the 

 same ossicle in the young of those genera or in the adult Priodon reminds the observer of 

 'Rhinoceros. This is at least remarkable when we remember the relationship of the 

 ossicula of the adults in some of the Ungulata to those of the young in others. 



In Priodon gigas (PI. LXIV. fig. 5) the malleus has a much less developed and less 

 globular head than in the above-described Armadillos : the articular surface is of similar 

 form ; the neck is thinner, longer, and straighter. The lamina is rather wide, and pro- 

 longed a little on the strongly decurved processus gracilis, which is joined by a styliform 

 process from the front of the head, which has its homologue in the Carnivora, Rodentia*, 

 Ungulata, Cetacea t, and most other Orders. The processus muscularis is wanting. 

 The manubrium forms little more than a right angle with the neck ; it is much more 

 slender than in Dasypus, and bent outwards on the rest of the malleus ; there is no pro- 

 cessus brevis, but, on the contrary, a very blunt projection at its site. The ill-developed 

 head, peculiar lamina, and the form of the manubrium give it a general resemblance to 

 the malleus of Mhinoceros. 



The incus of Priodon (fig. 5) has a shorter processus brevis than in Dasypus ; the long 

 crus is much stouter, and has a notch or fork on its upper margin. Hyrtl has observed 

 a similar appearance in the Sloths. The processus longus bears a distinct, sessile, and 

 very elliptical Sylvian apophysis. 



The stapes (fig. 5) has much stouter crura than in Dasypus or Tatusia, with a small 

 intercrural aperture. The base is rather narrow ; and in no wise does this ossicle bear 

 any resemblance to that of Dradypus or Manis. 



In the Three-banded Armadillo {Tolypeutes tricinctus, fig. 6), the malleus of the 

 adult much resembles that of Priodon ; but the lamina is very wide, so that the ossicle 

 is modified from a low type in the same direction as in the Carnivora, Artiodactyla, and 

 Muridse. The neck remains straight, and the outer angle of the base of the manubrium 



* See remarks on the malleus of the Musquash (Fiber). 

 t Description of the malleus of Balcena, anted. 



