The _T. swainsoni_ is found in abundance westward to the western limit of the Rocky Mountain system; in the latter region specimens at all seasons have the olive of a clearer, more greenish shade than in any Eastern examples; this clearer tint is analogous with that of the Rocky Mountain form of _pallasi_ (_auduboni_). In precisely the same region inhabited by the _pallasi_ var. _nanus_ the _swainsoni_ also has a representative form,—the var. _ustulatus_. This resembles in pattern the var. _swainsoni_, but the olive above is decidedly more rufescent,—much as in Rocky Mountain specimens of _T. fuscescens_; the spots on jugulum and breast are also narrower, as well as hardly darker in color than the back; and the tail is longer than in Rocky Mountain _swainsoni_, in which latter it is longer than in Eastern examples. The remaining species—_mustelinus_, _fuscescens_, and _aliciæ_—extend no farther west than the Rocky Mountains; the first and last only toward their eastern base, while the second breeds abundantly as far as the eastern limit of the Great Basin. The _T. fuscescens_, from the Rocky Mountains, is considerably darker in color above, while the specks on the throat and jugular are sparser or more obsolete than in Eastern birds. In _T. mustelinus_, the only two Western specimens in the collection (Mount Carroll, Ills., and Fort Pierre) have the rump of a clearer grayish than specimens from the Atlantic Coast; in all other respects, however, they appear to be identical. Some Mexican specimens, being in winter plumage, have the breast more buffy than Northern (spring or summer) examples, and the rufous of the head, etc. is somewhat brighter. In _aliciæ_, no difference is observed between Eastern and Western birds; the reason is, probably, that the breeding-ground of all is in one province, though their migrations may extend over two. There is, however, a marked difference between the spring and autumn plumage; the clear grayish of the former being replaced, in the latter, by a snuffy brown, or sepia tint,—this especially noticeable on wings and tail. [Illustration: PLATE I. 1. Turdus mustelinus, _Gm._ Penn., 1570. 2. “ ustulatus, _Nutt._ Oregon, 2040. 3. “ aliciæ, _Baird_. Illinois, 10084. 4. “ swainsoni, _Cab._ Penn., 981. 5. “ fuscescens, _Steph._ D. C., 28231. 6. “ pallasii, _Cab._ Penn., 2146. 7. “ nanus, _Aud._ Cala., 17997. 8. “ auduboni, _Baird_. Rocky Mts., 10886.] The following synopsis is intended to show the characters of the different species and varieties. 1. _Spots beneath rounded, covering breast and sides._ A. Rufous brown above, becoming much brighter toward the bill, and more olivaceous on the tail. Beneath white; whole breast with rounded spots. Nest on tree; eggs pale blue.