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



prominence were raised to the exact axial line of the head (for even in these cases the 

 manubrium is never literally in that axis, but always slightly bent on the head), the rest 

 of the handle retaining its angle, we should have an ossicle almost exactly like the 

 malleus of Ateles. The processus muscularis, placed so low down as the inner edge of 

 the manubrium, would then be brought close to the neck, its normal or, at least, most 

 usual position. 



The Ossictjla of the Lemtjrld^;. 



In the genus Lemur (PI. LVIII. fig. 21) the malleus has a well- developed head, rising 

 considerably above the level of the articular surface, which is tolerably deep, and much 

 like the same in the Old-world monkeys. A faint trace of a neck exists ; the manubrium 

 forms an angle of 150° with the rest of the ossicle, and ends in a broadly spatulate or 

 discoidal termination. In the specimens of L. varius and L. albifrom in the College 

 collection, the manubrium is much flattened near the base, as in Homo ; and in L. albi- 

 from sl distinct processus brevis exists ; but in L. catta, L. nigrifrons, and L. xanthomystax 

 the base of the handle is narrow, and hardly perceptibly flattened ; but probably in any 

 species of this genus a processus brevis may be occasionally developed. A small area of 

 lamellar bone is generally to be seen between the head and the stump of the processus 

 gracilis. The malleus of Lemur bears more resemblance to the same in the Old-world 

 monkeys than to the Ceboid type — not so, probably, from any nearer relation of the Lemurs 

 to the Macaques &c, which is most unlikely, but rather from the fact that the malleus 

 of the American monkeys is highly specialized, while it happens that the same in Lemur 

 and the tailed Old-world monkeys is of a far more generalized type in all cases. 



The incus decidedly varies in form in different species of Lemur. In the College 

 specimens of that bone in L. varius the body is wide horizontally and shallow vertically, 

 with stout widely divergent crura. In L. nigrifrons and L. xanthomystax the body is 

 both shallow and narrow, the crura stout and but little divergent, so that the ossicle has 

 a very tooth-like appearance. In L. albifrons and L. catta the body is square, and the 

 processus longus is slender and very divergent. 



The stapes has always long and extremely slender crura, very slightly bowed outwards, 

 with a wide aperture. The base is invariably convex towards the vestibule, and rather 

 narrow vertically. The space between the crura is in this genus always occupied by a 

 bony canal, which runs between two projections of the petrous bone above and below 

 the fenestra ovalis, and transmits a small blood-vessel — a frequent condition among some 

 Insectivora and Rodents. The same condition is seen in a skull of Hapalemur in the 

 Museum of the Royal College of Surgeons. 



Among the Indrisinse, Tropithecus (PI. LVIII. fig. 24) * has a malleus more like 

 that of Cebus than Lemur. The head is of much the same shape, and the articular 

 surface of the same depth, as in the latter ; but there is the same absence of all trace of 

 neck, so frequent in the American monkeys. The manubrium is sharply curved in the 

 middle, and terminates in a very large disk. The incus is wide horizontally ; the pos- 



* Sketched from a young specimen. The presence of the processus gracilis, with some friable tissue between it and 

 the neck, alters its aspect. 



