A male from Socorro Island (49,678, Colonel A. J. Grayson) is less adult than the preceding. The upper plumage is more brownish and more mottled; the rufous spots, though deeper and larger, are less sharply defined; the spots on the primaries are all ochraceous; the bands on the tail are broader, though of the same number. Beneath the longitudinal blotches do not appear, but the rusty rufous covers nearly the whole surface, leaving the medial portion only white, and this not well defined; the rusty shows ragged minute transverse bars of blackish. The whitish collar round the nape is also better defined than in the type. Wing, 4.20; tail, 2.10. Wing-formula, 4, 3=5–6, 2–7, 8, 9, 10, 1. Length, 5.20; extent, 14.25. Another specimen, 50,765, from the same locality, also apparently immature, is just like the preceding in plumage. It measures, wing, 4.00; tail, 1.90. [Illustration: _Micrathene whitneyi._] HABITS. The type specimen of this diminutive species was shot at Fort Mohave, in the Colorado Valley, latitude 35°, April 26, 1861, and two others have since been taken on the Socorro Islands, off the western coast of Mexico, by Colonel Grayson. It is smaller even than the little California Pygmy Owl, and is therefore the smallest known to inhabit North America. It resembles that species in its colors, but is thought by Dr. Cooper to be more similar to the burrowing Owls in its generic characters. It was found in a dense thicket, on a very windy morning, and where it may have taken only a temporary refuge, after having been blown down from some of the caverns in the barren mountains surrounding the valley. In its stomach were found the remains of insects and the feathers of small birds. Several specimens of this Owl were taken in Arizona by Captain Bendire, one of which is now in the collection of the Boston Society of Natural History. Captain Bendire also found one of their nests, with two fully fledged young ones, in a hole of a mesquite stump. GENUS SPEOTYTO, GLOGER. _Speotyto_, “GLOGER, 1842.” (Type, _Strix cunicularia_, MOL.) “_Pholeoptynx_, KAUP, 1848.” (Same type.) GEN. CHAR. Size small; head small, and without ear-tufts. Bill moderately strong, pale yellowish. Tarsi more than twice as long as the middle toe, feathered in front, naked behind; toes scantily haired. Tail short, less than half the wing, nearly even, or very slightly rounded. Three outer quills with their inner webs emarginated; second to fourth longest. Ear-conch very small, simple, roundish. Diurnal and terrestrial. [Illustration: =5896= ½ ½ _Speotyto hypogæa._]