Saxicolidæ. Wings very long and much pointed, reaching beyond the middle of the short square or emarginated tail, and one and a half times or more the length of the latter. The spurious primary very short, the second quill longer than the fourth. In the closed wing the outer secondary reaches only about two thirds the length of longest primary. Turdidæ. Wings moderate, more rounded, not reaching beyond middle of the often rounded tail, and not more than one and a third the latter, usually more nearly equal. Spurious primary sometimes half the length of second quill; the second quill shorter than the fourth. In the closed wing the outer secondary reaches three fourths or more the length of longest primary. B. Nostrils linear, in lower edge of nasal membrane. Loral and frontal feathers soft and downy, and no bristles or bristly points whatever about the mouth. Cinclidæ. Body very short and broad. Wings short, rounded, and concave. The American _Sylviidæ_ are in some respects very closely related to the _Saxicolidæ_, but may be distinguished by their much smaller size, more slender and depressed bill, more strongly bristled rictus, etc.; on which account they are more strictly “fly-catchers,” taking their prey in great part on the wing. Of the three families, the _Turdidæ_ contain a great variety of forms, and exhibit widely different characters, rendering it exceedingly difficult to arrange them in any systematic or regular sequence, or to accurately define their boundaries. In the _Birds of North America_, the Mocking Thrushes were placed among the Wrens, on account of the distinct tarsal scutellæ, and other characters. We are now, however, inclined to believe, with Dr. Sclater, that their place is with the recognized _Turdidæ_; and, among other reasons, on the ground of their more deeply cleft toes, and greater extension forward of frontal feathers. The following synopsis of the North American forms will serve the purpose of determining the genera, even if these are not arranged or combined in a strictly natural manner. A. Turdinæ.—Tarsus covered anteriorly with a continuous plate without scales. Wings decidedly longer than the tail, which is nearly even. Bill considerably shorter than the head. First quill usually not one fourth the second. Wings pointed. Tarsus hardly the length of head, but yet longer than middle toe; outstretched toes falling short of tip of tail … _Turdus_. B. Miminæ.—Tarsi scutellate anteriorly; scales seven. Wings decidedly longer than the tail, which is nearly even. Tarsus as long as the head. Bill decidedly shorter than the head, scarcely notched; wings pointed; first quill less than half the second, third and fourth longest. Claws not peculiar. Bristles prominent. Tarsus considerably longer than middle toe and claw … _Oreoscoptes_.