In their distribution, the Owls, as a family, are cosmopolitan, and most of the genera are found on both hemispheres. All the northern genera (_Nyctea_, _Surnia_, _Nyctale_, and _Scotiaptex_), and the majority of their species, are circumpolar. The genus _Glaucidium_ is most largely developed within the tropics, and has numerous species in both hemispheres. _Otus brachyotus_ and _Strix flammea_ are the only two species which are found all over the world,—the former, however, being apparently absent in Australia. _Gymnoglaux_, _Speotyto_, _Micrathene_, and _Lophostrix_ are about the only well-characterized genera peculiar to America. _Athene_, _Ketupa_, and _Phodilus_ are peculiar to the Old World. The approximate number of known species (see Gray’s Hand List of Birds, I, 1869) is about two hundred, of which two, as stated, are cosmopolitan; six others (_Surnia ulula_, _Nyctea scandiaca_, _Glaucidium passerinum_, _Syrnium cinereum_, _Otus vulgaris_, and _Nyctale tengmalmi_) are found in both halves of the Northern Hemisphere; of the remainder there are about an equal number peculiar to America and the Old World. As regards the distribution of the Owls in the Nearctic Realm, a prominent feature is the number of the species (eighteen, not including races) belonging to it, of which six (_Micrathene whitneyi_, _Nyctale acadica_, _Syrnium nebulosum_, _S. occidentale_, _Scops asio_, and _S. flammeola_) are found nowhere else. _Speotyto cunicularia_ and _Bubo virginianus_ are peculiarly American species found both north and south of the equator, but in the two regions represented by different geographical races. _Glaucidium ferrugineum_ and _G. infuscatum_ (var. _gnoma_) are tropical species which overreach the bounds of the Neotropical Realm,—the former extending into the United States, the latter reaching to, and probably also within, our borders. Of the eighteen North American species, about nine, or one half (_Strix flammea_ var. _pratincola_, _Otus brachyotus_, _O. vulgaris_ var. _wilsonianus_, _Syrnium cinereum_, _Nyctale acadica_, _Bubo virginianus_, and _Scops asio_, with certainty, and _Nyctea scandiaca_ var. _arctica_, and _Surnia ulula_ var. _hudsonia_, in all probability), are found entirely across the continent. _Nyctale tengmalmi_, var. _richardsoni_, and _Syrnium nebulosum_, appear to be peculiar to the eastern portion,—the former to the northern regions, the latter to the southern. _Athene cunicularia_ var. _hypugaea_, _Micrathene whitneyi_, _Glaucidium passerinum_ var. _californicum_, _Syrnium occidentale_, and _Scops flammeola_, are exclusively western, all belonging to the southern portion of the Middle Province and Rocky Mountain region, and the adjacent parts of Mexico, excepting the more generally distributed _Speotyto cunicularia_, var. _hypogæa_, before mentioned. Anomalies in regard to the distribution of some of the species common to both continents, are the restriction of the American