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



gracilis represents the lamina so marked in the other Artiodactyla ; it exists in the 

 same modified form in the still larger malleus of the Elephant. 



The incus has a very high and rather narrow body ; the upper part of the articular 

 surface is very hroad, the lower part forms a deep, narrow groove, to fit the lower facet 

 of the malleus. Both crura are very short and divergent ; there is a small tubercle 

 over the outer aspect of the processus longus, which crus is concave on its inner side. 

 This high-bodied incus is thoroughly porcine. The stapes has a comparatively small 

 head, with a fia/t tubercle on its posterior side for the stapedius tendon. The crura 

 are both straight, the posterior is much thicker than the anterior, and they diverge very 

 considerably, leaving a large space between them. The base is thin, broad, and rather 

 convex ; the whole bone forms an equilateral triangle. Hyrtl considers the aperture 

 between the crura to be small ; but it is very wide in three stapedes of Hippopotamus 

 in the College collection. 



In the Wart-Hog {Phacochcerus cethiopicus) the malleus resembles that of Sits, about to 

 be described ; but the following distinctions exist : 1, the upper part of the head is narrower, 

 and projects more prominently forwards ; 2, the articular surface is wider and shallower, 

 the lower facet is nearly as large as the upper, both are only slightly and evenly 

 saddle-shaped, and the groove between them is very faint instead of being sharply cut. 

 This is a distinct approach to the Hippopotamus. The manubrium is almost straight 

 towards the extremity. The incus is like that ofSus, except that the processus " brevis" 

 is absolutely longer than the stapedial crus, and is slender and blunt-pointed. The 

 stapes is pig-like ; its crura are extremely slender. 



In the Suid^e (PI. LXI. fig. 6) the malleus is of the broadly laminate type. The head 

 is well developed, though not so large proportionally as in the Hippopotamus, and 

 projects forwards rather than upwards ; the articular surface is narrow and deep. The 

 groove dividing the facets is very sharply defined ; the upper is larger than the lower ; and 

 both are saddle-shaped, a vertical convex ridge running near their outer borders, leaving 

 to each a very narrow outer segment, — a very different condition from that which exists 

 the Carnivora, where the malleus is of a very similar form. The neck is very narrow, 

 and boldly curved ; a stout lamina connects it with the thin processus gracilis. From 

 the inner aspect of the neck, a slight distance from the root of the handle, springs a long, 

 stout, and straight processus muscularis, similar to that of the Hippopotamus. The 

 manubrium leaves the neck almost at a right angle ; it is not very broad laterally at the 

 base, and has a sharp processus brevis pointing vertically upwards. Its outer aspect 

 has well-defined borders, but is very narrow ; the extremity turns up slightly, but dis- 

 tinctly, and is but little dilated. 



The incus has a well -developed exceedingly square body, with short processes, as in 

 Phachochosrus and Hippopotamus, and contrasts strongly with the incus of the Ox and 

 Deer, and still more with that of the Perissodactyla. Its articular surface is deeply cut, 

 to fit that of the malleus ; the lower facet is narrow and shallow, a natural and necessary 

 variation from the same in the Hippopotamus, corresponding to a similar difference in 

 the malleus. The stapedial crus is scarcely longer than the processus brevis, and sup- 

 ports a small, discoid, pedunculated Sylvian apophysis. The stapes tends to the quadri- 



