476 MR. A. H. G. DORAN ON THE MORPHOLOGY 



base, than in the two larger Ant-eaters. The whole bone somewhat resembles the same 

 ossicle in Bradypus. The incus has a shallow body ; and the end of its stapedial eras bears 

 a very elliptical and sessile Sylvian apophysis, so narrow vertically as to be almost 

 rod-like. The stapes in a young specimen in the Collection has no trace of any division 

 between the crura, and in general resembles that ossicle in the Sloths. 



In the Ant Bear ( Orycteropus cethiopicus, PI. LXIV. fig. 14) the head of the malleus 

 is ill-developed, the articular surface is shallow and wide vertically, both facets are but 

 faintly convex. The neck is long and curved ; it bears internally and nearly one line 

 distance from the root of the handle a prominent tubercular processus muscularis. There 

 is a wide and transparent lamina. The manubrium is very long, and forms a right angle 

 with the body ; it is rather broad at the base, and presents an angle corresponding to the 

 processus brevis ; the extremity is very little dilated or recurved. In the characters of the 

 head the malleus of the Aard-vaark ( 0. capensis) resembles Priodon ; but the greater 

 length of the manubrium, the broad lamina, and the very distinct processus muscularis 

 distinguish it readily from the latter. 



The body of the incus is shallow ; both crura are long and divergent ; the Sylvian apo- 

 physis is almost obsolete, being only separated from the long crus by an indistinct 

 groove. 



The stapes has an ill-developed head, and two long slender crura bowed outwards ; a 

 thin bony lamina is spread between them below, closing the lower part of the aperture, 

 which otherwise would be wide. The foot-plate is not very wide horizontally, and is narrow 

 vertically. Hence the stapes of Orycteropus, on account of the latter feature, is of a 

 still higher type than that of Myrmecophaga. 



Reviewing, then, the ossicula of the Edentata as a whole, it may be asserted : — 



I. That in the Bradypodidae the characters of the malleus and incus are fairly gene- 

 ralized, whilst the stapes assumes to a certain extent, though never completely, Sau- 

 ropsidan characters. Choloepus differs from Bradypus in the form of the malleus. 



II. That in the Loricata the genera Basypus and Tatusia present much higher cha- 

 racters in their ossicula than are found in Priodon and Tolypeutes. In the first two 

 genera the stapes is of a high type, both as to its crura and its base ; in Priodon that 

 ossicle is more Sloth-like ; in Tolypeutes it resembles that of the Kangaroos and other 

 Marsupials, or even some Birds, but not the complete columelliform type of Manis and 

 most Aves. 



III. Manis has the most positive characters of interest to be found among all Edentata : 

 the malleus is more specialized than in the other groups ; the incus has peculiar though 

 less unusual characters ; and the stapes is more absolutely Sauropsidan in every respect 

 than in any other placental mammal. 



IV. In the Ant-eaters the malleus may be known from that of other Edentata by the 

 form of its head. The stapes is of as high type, as to the free separation of its crura, as 

 that of Basypus ; but the base has a tendency to assume the circular rather than oval, 

 form seen in the columella of Birds. Cyclothurus, in its malleus, tends more towards 



