178 EAR 



noticed here a small gi'oup of Eagles, characterized, by their long 

 legs, forming the genus Nisaetus, of which one species, N. fasciahiS 

 or honellii, is found in Europe. The OsPREY (Pandion), though 

 placed by many among the Aquiline, certainly does not belong to 

 that subfamily. 



EAR. The whole auditory apparatus is divided into the outer, 

 middle, and inner ear. 



The outer ear or " auditory meatus " is a short, membranous, and 

 sometimes partly cartilaginous tube. The outer opening is generally 

 covered by feathers, and rarely naked as in Vultures and Ostriches. 

 The feathers which surround the ear are often more or less reduced, 

 and occasionally assume the shape of bristles. There is no external 

 ear or " concha auris," but a more or less prominent fold projects 

 from the outer margin into the meatus, and seems to be used as 

 a sort of imperfect valve, especially since it possesses several little 

 muscles. Such a valvular fold attains its largest development in 

 Owls. Many of these birds present the peculiar anomaly of 

 having the outer ears very asymmetrically developed, an asym- 

 metry which often affects also the whole of the temporal region 

 together with the scjuamosal, quadrate, and neighbouring bones, 

 so that the whole skull assumes a lop - sided shape. Collett 

 {Christiania Videnskahs. Forhandl. 1881, No. 3, pp. 1-38, pis. i.-iii.) 

 has examined this point in all the North-European species of Owl. 

 According to him there are three different formations : 1. Skull 

 and auditory meatus symmetrical, ear-valve absent : Surnia 

 funerea, Glaucidium passerinum, Nyctea scandiaca. Bubo ignavus. 

 2. Skull symmetrical, meatus asj^mmetrical, ear- valve present : Asio 

 accipitrinus, A. otus, Strix aluco. 3. Skull and meatus asym- 

 metrical, ear- valve present : Strix uralensis, S. lapponica, and 

 Nyctala tengmalmi. Of other, riot North -European, Owls, Aluco 

 flammeus belongs to the first group. ^ 



Another peculiar modification is exhibited by the Capercally. 

 It is well kno^vn that the cock for several seconds towards the end 

 of his rutting ecstasy is completely deaf to any external sounds. 

 This deafness is produced by an erectile fold of the posterior wall 

 of the auditory meatus ; this fold or flap becomes turgid with 

 blood during the excitement of the bird, and seems moreover to 

 be assisted in pressing upon the opposite margin of the quadrate 

 bone, and in thus effectively closing the ear-passage, by the action 

 of the digastric or depressor muscle of the mandible which is 

 always widely opened during this stage. The harsh and loud 

 sounds emitted by the cock, and the blocked ear-passage render 

 him absolutely indifferent to any other sounds. (See Graff and 



1 A large number of figures of North- American species in illustration of this 

 point is given by Ridgway {North American Birds, iii. pp. 97-102). 



