OF THE MAMMALIAN OSSICULA AUDITUS. 417 



In the Guinea-pig ( Cavia caprera, PL LX. fig. 33) the malleus and incus, which are 

 ankylosed in new-born specimens, resemble strongly those of Dolichotis ; but the head of 

 the malleus is more produced and more slender. The manubrium has the same general 

 characters ; only its thin flattened sides and spatulate extremity are much broader than 

 in the Patagonian Cavy ; there is a distinct trace of a processus brevis. The stapes has 

 all the characters seen in Dolichotis; there is sometimes a bony canal between its 

 crura. 



In Si/drochcerus capybara (PL LX. fig. 32) the malleus and incus are ankylosed in the 

 adult, but often free in young skulls. The head of the malleus is stout and less produced 

 than in Cavia and Dolichotis ; and the manubrium mostly resembles the same in the 

 latter. The crura of the stapes are long, rather crooked, and slightly divergent ; the 

 base is somewhat narrow, stout, and extends beyond the insertions of the crura. No 

 bony intercrural canal exists, or at least it is not constant. 



Among the Glires Duplicidentati, the Lepokld^: possess a malleus which does not 

 assume the extreme types seen in different Rodents, such as the Sciuridse and the 

 Hystricomorpha. It assumes the less-specialized characteristics of the Marmots, Bears, 

 and some of the Muridse. 



In the English Hare [Lepus europceus, Pallas) the head of the malleus is ill developed, 

 rising hardly at all above the articular surface ; however, it sends a narrow projection 

 towards the trace of the lamina. The articular surface is rather deeply cut, and rather 

 narrow laterally ; the facets have a vertical convex ridge across their middle as in many 

 animals in other orders. Between the body and the processus gracilis is a very fragile 

 and rather narrow bony lamina, generally damaged in the removal of the bone, but plainly 

 visible if the malleus of a new-born hare or rabbit be prepared in situ with the tympanic 

 bone. I have examined it in its natural position in the adult hare and rabbit, 

 and certainly have found the lamina partially absent. That it should atrophy during 

 adolescence is highly probable, seeing that the processus gracilis itself is partially absorbed 

 in Man and in many lower animals. 



The neck of the Hare's malleus is very distinct, being much constricted and rather 

 short. The manubrium is of the sword-shaped form seen in the Beaver, being very thin 

 and flattened laterally, broad at the base, and well recurved. There is a trace of pro- 

 cessus brevis (PL LX. fig. 34, L. cuniculus, p b) ; the muscular process (p m) is situated 

 on the inner border very close to the neck. The outer edge is very narrow, though 

 distinctly bordered off from the sides and hardly dilated at the tip. This broad manu- 

 brium, without an angle on its inner margin, may be considered a central type among 

 Rodents, differing, on the one hand, from the narrower manubrium of the typical 

 Squirrels, and, on the other, from the trapezoidal handle of the malleus in the Hystri- 

 comorpha. 



The incus has an ill-developed posterior crus and a very divergent stout processus 

 longus, bearing a well-developed elliptical and pedunculated Sylvian apophysis. Of 

 course the articular area is deeply cut ; otherwise, particularly in the crura, this ossicle 

 resembles the same in most Eats and Squirrels. 



