EXTERNAL ANATOMY. EARS. 
47 
below, we must be allowed to question the accuracy of 
the statement: it wears every appearance of exaggera- 
tion, and obviously cannot be proved. That most of 
the rapacious tribes, on the other hand, possess a length 
of sight, if we may use the term, far superior to ah. other 
birds, is proved by the additional means given to them 
for that purpose, in the structure of the eyebrows, or 
superciliary ridge, which, in these birds, projects over 
the eyes, to w'hich they act as a screen from the vertical 
rays of light, and concentrates their powers in viewing 
objects placed before or beneath them. This structure is 
also apparent in the horned owls and eagle owls (Otus, 
Nyctea), but is not found in those of the restricted genus 
Strix. 
(51.) The Ears of birds, excepting those of the owls, 
exhibit to outward appearance very Mttle variation. M. 
Cuvier remarks, that nocturnal birds alone have a large 
external ear, which nevertheless is not so prominent as 
that of quadrupeds. This statement is so vague as to 
require some explanation. The ears of a sparrow or a 
hawk are just as external as those of an owl, seeing 
that in neither of these birds can they be discovered 
unless the feathers are carefully removed ; whereas, when 
we speak of an external ear, 
we annex the idea of its being 
prominent, Mke that of the 
majority of quadrupeds. Now, 
there is only one bird yet dis- 
covered, whose ear, in this 
sense, can be called external ; 
and this is theL’Oricoii of Le 
Vaillant* {J!g.2\.), a large 
species of vulture, discovered 
by him in Southern Africa, 
and subsequently named by methodists Vultur auricu- 
laris; the ear, in this singular hird, appears truly external, 
* Ois. d'Afrique, vol. i. pi. 9. Some ornithologists arc of opinion that 
this iirolongation is the mere effect of leanness, or of old age, as wnuklcs 
are on the human face j but thU theory wants confirmation. 
