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



The incus in an adult sheep has a well-developed body, which is by no means shallow, 

 but never as square and solid as in the Pigs and their allies. The great development of 

 the crura in Ovis makes the body look smaller than it really is. The processus " brevis " 

 is very long and straight, and almost cylindrical in form, though a little compressed 

 vertically. The processus "longus," well divergent from the other eras, is absolutely 

 shorter ; it bends very abruptly above its termination, which bears a very well-formed 

 pedunculated and perfectly elliptical Sylvian apophysis. In the incus of a new-born lamb 

 (PI. LXI. fig. 17) the body is much shallower, as in many less typical Bovidse ; that part 

 of the same ossicle in the adult sheep, on the other hand, clearly approaches the high 

 well-developed type seen in adult oxen. 



The stapes in a large adult skeleton is quite trapezoidal; the head is large and square, 

 bearing a slight trace of a process for the insertion of the stapedius muscle on its inner 

 aspect. The crura are thick and deeply channelled towards the aperture ; they are wide 

 apart at their origin and almost parallel ; the anterior is the thinner and longer ; so that 

 base is further from the head in front than behind. The base is thick, its upper border 

 is strongly arched, and both extremities project very perceptibly beyond the insertion of 

 the crura. 



But in the new-born lamb the stapes is generally quite triangular, the head being 

 much less developed, and the crura close together at their insertion. It will be seen to 

 retain features observable among many adult Antelopes — that ossicle in the Sheep, when 

 full-grown, approaching, as does the incus, the type seen in Bos. 



The Ox will now be considered ; and it will be demonstrated afterwards how every grade 

 of transitional features in all the ossicula, between Ovis and Bos compared, are seen in 

 every kind of combination in Goats and Antelopes. 



In a malleus taken from a large Ox's skull (PI. LXI. fig. 14) the head appears no more 

 developed above the facets than in Ovis ; but the articular surface, wide horizontally, is 

 very wide vertically, the facets gaping far apart. The upper is almost plane, though 

 still slightly convex ; the lower is more perceptibly elevated, and is divided from the 

 upper by a very faint groove. The neck is short and very strongly curved ; the lamina 

 is moderately wide ; the processus muscularis projects from the inner side of the neck 

 some distance from the manubrium, and is rather short, almost straight, and blunt- 

 pointed. The manubrium is boldly curved, with the concavity forwards; its outer 

 aspect is rather broad and sharply bordered, dilating but little and very gradually 

 towards the tip. The base projects upwards, outwards, and a little backwards, and may 

 be said to bear a true processus brevis. 



The malleus of a foetal calf at the sixth week (PI. LXI. fig. 15), on the other hand, 

 is much more like that of an adult Sheep, and is almost as large. The articular surface 

 is wide and deep vertically, as in Ovis, but not so deep as in the adult Bos ; and the 

 facets are more perceptibly convex. The manubrium too is almost straight, and slightly 

 recurved at the tip, instead of being well bowed forward. In the mature foetus the 

 malleus has assumed the adult Ox's character. 



The incus in the full-grown Bos has a very well-developed body, its outer and inner 

 aspects both showing a wide, convex, bony surface ; the postero-superior border over 



