VI STRIGIDAE 399 
eyes are directed obliquely forwards, but those of Vinow are said 
to have a less staring look; Owls, moreover, have little power of 
turning the eye-ball, and consequently add to their grotesque 
appearance by constantly moving the head from side to side. 
The upper eye-lid shuts over the eye, and not the lower, as in 
birds generally ; the iris is extremely sensitive, contracting and 
expanding continually. The external ear varies in an extra- 
ordinary way, the “conch,” or large shell-like aperture, often 
having its ample membranous margin developed into an elevated 
operculum or flap which stretches partially or entirely down the 
anterior side. In Asio and Syrnium the ear-openinges are asym- 
metrical, those of the former reaching nearly the whole height 
of the skull and being directed respectively wpwards and down- 
wards; in Nyctala this asymmetry extends to the bones of the 
skull itself The large ear is apparently correlated with a keen 
sense of hearing in some cases, but not in all. 
The furcula, when complete, is U-shaped; the tongue is fleshy, 
and somewhat horny below; the nostrils, placed towards the 
front of the cere, are rather large, and usually concealed by 
bristles; the syrinx is bronchial; the after-shaft is absent or 
rudimentary ; down occurs in the adults only on the unfeathered 
spaces, but in the nestlings forms a woolly coating, which may be 
brown or dusky, as in the Snowy Owl, white as in the Screech- 
Owl, yellowish or grey, as in many species. 
The sexes are alike, the female being larger than the male. 
The young resemble the adults, but, at least in certain cases, are 
more rufous or buff; further information is, however, needed as to 
the successive stages. All Owls exhibit a certain similarity, while 
their ample plumage creates an erroneous impression of bulk ; 
the feathers—most compact in Surnia—are soft, with an admix- 
ture of hairs and with weak, brittle shafts, to which facts the noise- 
less flight is largely due. An erectile tuft decorates each side of 
the crown in Bubo, Asio, Scops, and Ketupa ; but the most strik- 
ing outward characteristic is the ruff of several series of small, 
stiffshafted, recurved feathers, originating from a fold of the skin 
round the cheek, which support the larger feathers of the over- 
lying “disc” around the eye. The latter is very complete in Striz, 
Syrnium, and Asio, being in the first-named rather triangular 
than circular; but in Surnia, Speotyto, Bubo, and Scops, not to 
mention other cases, it is far less perfect. 
