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



alike remarkable for the small size of the species, namely the Muridse and Soricidas. 

 There may be some functional explanation of this similitude. 



Among the VESPERTiLiONiDiE, the malleus of Plecotus auritus (PL LXII. fig. 21) closely 

 resembles that of Asellia; but the lower process (fig. 20, acpm) is absent. The extremity 

 of the manubrium is rather widely spatulate. 



The stapes has long crura, both almost straight ; unlike most Bats, they diverge but 

 little ; the aperture is on that account long and narrow ; it is not occupied, in the recent 

 skull, by any bony canal. 



In Vesperugo serotinus (PL LXII. fig. 25) tbe malleus also much resembles that of 

 Asellia ; the upper or true processus muscularis alone exists, so that we miss the lower, 

 which in Asellia sends a conspicuous buttress from its base across the lamina. The 

 orbicular apophysis is smaller and more pointed in Vesperugo. 



The incus of Vesperugo has a well-formed body, deeply excavated by the articular 

 surface ; the processus brevis is short, but stout ; the processus longus is very long and 

 divergent ; it is slightly grooved on its upper and anterior aspect, and ends in an almost 

 discoid Sylvian apophysis, mounted on a very slender peduncle. In general characters 

 this incus is of a low type ; the same form is frequent among Marsupials. In all the 

 insectivorous Bats the body of the incus is deeper and better developed over the pro- 

 cessus longus than it is over the shorter crus. The minute stapes of Vesperugo has a 

 small broad head, with a tubercle on its posterior aspect. The crura are slender and 

 very divergent ; the posterior is quite straight, the anterior a little curved. The aperture 

 is very wide ; the base has a rather thick border, so as to be slightly concave towards the 

 vestibule. It is much narrower anteriorly than behind — a well-marked feature here, 

 seen to a less extent in the stapes of Homo, and still less distinctly in most mammals. 



The completely bicrurate stapes of these small Chiroptera, with a moderate or wide 

 aperture, is interesting when we consider the low type of the other two ossicula ; but the 

 wideness of the aperture may not so much indicate high type, but may be considered as 

 merely due to the passage of an artery * between the crura ; the same remark, as I have 

 already observed, applies to many Insectivora where the stapes has a wide aperture. 

 Whether a vessel passes through the opening free or unsupported by a bony canal is of 

 small moment ; still some may consider the wideness of the aperture as a sign of high 

 type, since in Lemur, where a bony canal exists, the crura do not diverge widely ; so that 

 in the Bats and Shrews the wideness may not be entirely for the benefit of the canal or 

 artery, especially as these structures do not always completely block up the aperture. 

 In many Bodents I have found the blocking complete without the crura being much 

 bowed or very divergent, as in some skulls of Gapromys. 



The malleus of Vespertilio nattereri (PL LXII. fig. 22) is very similar to that of Ves- 

 perugo. The processus muscularis, too, in this Bat, seems in position to be the homo- 

 logue of the upper process in Asellia, especially as, in the place of the lower distinct 

 process in the latter, I observe in Vespertilio a faint eminence which sends a pro- 



* See Hyrtl, op. cit. pi. ii. fig. 13. This artery is givon off from the carotid together with the occipital. 



