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



both inserted some distance from the extremities of the base, which is slightly convex 

 towards the vestibule. 



The crura are longer than in most Cebidse, where the stapes closely resembles that of the 

 Old-world monkeys, only differing from them, as a rule, in the greater length of their 

 limbs ; hence this distinctive feature of the entire family is best marked in Ateles. 



In the Howlers {Mycetes) the head of the malleus is of the same form as in Ateles, 

 but still more flattened vertically and still less developed, the height of its convexity 

 ^hardly rising above the level of the upper border of the articular surface (PI. LVIII. 

 fig. 14). This latter is extremely wide in all directions and very shallow; both facets 

 are very saddle-shaped. There is absolutely no neck ; but immediately from below the 

 articular aspect springs the manubrium, which is tolerably long, forms an even, rather 

 wide curve, and becomes gradually narrower towards the extremity, which ends in a 

 perfect disk. There is not a trace of a processus brevis ; and the processus muscularis is 

 almost obsolete. In M. seniculm the manubrium runs almost in the axis of the body ; 

 in M. laniger and M. ursinus it forms a distinct angle. 



The malleus of Mycetes, so different from that of Ateles, where there is a thick neck 

 and a manubrium bulbous in the middle and possessing a tubercular processus brevis, 

 may be considered a good type of this bone among the Cebidae, and to a certain extent 

 among the less-typical Lemurs. It differs strikingly from the same bone in Man, Apes, 

 Old-world monkeys, and the genus Lemur. 



The incus is very deep vertically, and narrow horizontally, with thick and short crura 

 arising close to one another. The articular surface has the peculiarity noticed in Ateles. 

 This bone, too, is very typical among the Cebidse. 



The stapes is of the ordinary monkey type, the base concave laterally, with a trace of 

 an umbo in a specimen of M. laniger in the College collection, but not in one of M. ursinus, 

 where the crura are almost fused ; a minute aperture which exists between them is, I have 

 reason to believe, accidental *. 



In Gebus (PI. LVIII. fig. 15) the malleus differs little from that of Mycetes ; the head 

 is almost identical in form. The manubrium runs still more closely to the axis of the 

 body ; and no rudiments of a processus brevis or muscularis can be traced. The handle 

 does not form the free and regular curve seen in most Howling-monkeys {Mycetes), but 

 is slightly bent near its root, and straighter towards its extremity, which is a little turned 

 up and almost a perfect disk. . 



. The incus departs from the type of Mycetes, Pithecia, Nyctipithecus and the Marmosets, 

 the body being generally longest horizontally, or quite square. The posterior crus is 

 rather thick at the base ; it diverges, as in most Cebidse, very little from the body. The 

 processus longus is often long and thin, and always divergent. 



The stapes is of the usual monkey form ; but in most specimens the posterior crus is 

 always slightly bowed and thicker than the anterior. 



In the Douroucoulis (Nyctipithecus, PL LVIII. fig. 16) I do not find any distinction 



* " Bei den Briillaffen ist die Basis konkav, aber in der Mitte als Umbo gegen das Vestibulum vorgetrieben. Bei 

 einem Sapajou dessen Species unbestimmt ist, finde ich in beiden Ohren die Crura des Stapes verwachsen." — Htrtl, 

 op. cit. But I have noticed an Umbo in an ape (see Hylobates). 



