On the North American continent the only widely distributed species which do not vary perceptibly with the region are _Otus brachyotus_ and _O. vulgaris_ (var. _wilsonianus_). _Bubo virginianus_, _Scops asio_, and _Syrnium nebulosum_ all bear the impress of special laws in the several regions of their habitat. Starting with the Eastern Province, and tracing either of these three species southward, we find it becoming gradually smaller, the colors deeper and more rufous, and the toes more scantily feathered. _Scops asio_ reaches its minimum of size and maximum depth of color in Florida (var. _floridana_) and in Mexico (var. _enano_). Of the other two I have not seen Florida specimens, but examples of both from other Southern States and the Lower Mississippi Valley region are much more rufous, and—the _S. nebulosum_ especially—smaller, with more naked toes. The latter species is darkest in Eastern Mexico (var. _sartori_), and most rufescent, and smallest, in Guatemala (var. _fulvescens_). In the middle region of the United States, _Scops asio_ (var. _maccalli_) and _Bubo virginianus_ (var. _arcticus_) are more grayish and more delicately pencilled than from other portions. In the northwest coast region they become larger and much more darkly colored, assuming the clove-brown or sooty tints peculiar to the region. The var. _kennicotti_ represents _S. asio_ in this region, and var. _pacificus_ the _B. virginianus_. The latter species also extends its range around the Arctic Coast to Labrador, and forms a northern _littoral_ race, the very opposite extreme in color from the nearly albinescent examples of var. _arcticus_ found in the interior of Arctic America.