The crania of the Owls present many features of interest, which may serve a good purpose in the definition of the sections and the genera, and to which attention has been occasionally called in the preceding pages. The tendency to asymmetry is especially marked in some species, and the better to illustrate this and other features we append several plates, in which the corresponding views are placed side by side.[39] The figures and accompanying lettering tell their own story, without any necessity of a labored description. R. R. [Illustration: _Syrnium aluco_ (copied from KAUP).] [Illustration: _Athene noctua_ (from KAUP).] [Illustration: _Nyctale richardsoni._] [Illustration: 7449. Strix pratincola. Natural size. 4886. Otus wilsonianus. Natural size. 7272. Scotiaptex cinereum. Two thirds. 7899. Nyctale richardsoni. Natural size. 414. Scops asio. Natural size. 773. Bubo virginianus. Two thirds. 628. Nyctea nivea. Two thirds. 7897. Surnia ulula. Natural size. 428. Glaucidium ferrugineum. Natural size. 437. Spheotyto hypogæa. Natural size.] [Illustration: 7449. Strix pratincola. Natural size. 4886. Otus wilsonianus. Natural size. 7272. Scotiaptex cinereum. Two thirds. 7899. Nyctale richardsoni. Natural size. 414. Scops asio. Natural size. 773. Bubo virginianus. Two thirds. 628. Nyctea nivea. Two thirds. 7897. Surnia ulula. Natural size. 428. Glaucidium ferrugineum. Natural size. 437. Spheotyto hypogæa. Natural size.] [Illustration: 7449. Strix pratincola. Natural size. 4886. Otus wilsonianus. Natural size. 7272. Scotiaptex cinereum. Two thirds. 7899. Nyctale richardsoni. Natural size. 414. Scops asio. Natural size. 773. Bubo virginianus. Two thirds. 628. Nyctea nivea. Two thirds. 7897. Surnia ulula. Natural size. 428. Glaucidium ferrugineum. Natural size. 437. Spheotyto hypogæa. Natural size.] [Illustration: 7449. Strix pratincola. 4886. Otus wilsonianus. 7272. Scotiaptex cinereum. 7899. Nyctale richardsoni. 414. Scops asio. 773. Bubo virginianus. 628. Nyctea nivea. 7897. Surnia ulula. 428. Glaucidium ferrugineum. 437. Spheotyto hypogæa. (All natural size.)] [Illustration: 12088. Nyctea nivea. (Ear copied from Swainson, F. B. A) 504. Scotiaptex cinereum. 49808. Surnia ulula. (Ear copied from Swainson.) A. Brachyotus “cassinii.” (Left ear and nostril, from fresh specimen.)] FAMILY FALCONIDÆ.—THE FALCONS. CHAR. Eyes directed laterally, and eyelids provided with lashes. Toes invariably naked, and tarsus usually naked and scutellate (feathered only in _Aquila_ and _Archibuteo_). Outer toe not reversible (except in _Pandion_). Head never with ear-tufts, and never wholly naked (except in the _Vulturinæ_, of the Old World).