In conclusion, I would say that the sole distinguishing character between the Peregrines from America and those from Europe, that can be relied on, appears to be found in the markings on the breast in the adult plumage; in all the specimens and figures of var. _communis_ that I have seen, the breast has the longitudinal dashes very conspicuous; while, as a general rule, in _anatum_ these markings are entirely absent, though sometimes present, and occasionally nearly as distinct as in European examples. Therefore, if this conspicuous streaking of the breast is found in all European specimens, the American bird is entitled to separation as a variety; but if the breast is ever immaculate in European examples, then _anatum_ must sink into a pure synonyme of _communis_. The var. _melanogenys_ is distinguished from both _communis_ and _anatum_ by the black auriculars, or by a greater amount of black on the side of the neck, and by more numerous and narrower bars on the under surface. In the former feature examples of _anatum_ from the southern extremity of South America approach quite closely to the Australian form, as might be expected from the relative geographical position of the two regions. The var. _minor_ is merely the smaller intertropical race of the Old World, perhaps better characterized than the tropical American form named _F. nigriceps_ by Cassin, the characters of which are so unimportant, and withal so inconstant, as to forbid our recognizing it as a race of the same rank with the others. LIST OF SPECIMENS EXAMINED. National Museum, 45; Boston Society, 4; Philadelphia Academy, 22; Museum Comp. Zoöl. 5; New York Museum, 3; G. N. Lawrence, 6; R. Ridgway, 3. Total, 88. _Measurements._ +----+-----------+-----------+---------+---------+-----------+----------+ |Sex.| Wing. | Tail. | Culmen. | Tarsus. |Middle Toe.|Specimens.| +----+-----------+-----------+---------+---------+-----------+----------+ | ♂ |11.30–13.00| 6.00–7.50| .75–0.80|1.60–1.90| 1.78–2.05| 29 | +----+-----------+-----------+---------+---------+-----------+----------+ | ♀ |13.00–14.75| 7.30–9.00| .85–1.00|1.95–2.10| 1.95–2.20| 28 | +----+-----------+-----------+---------+---------+-----------+----------+ Var. pealei, RIDGWAY. BLACK PEREGRINE FALCON. _? ? Accipiter falco niger_, BRISS. Orn. I, 337. _? ? Falco niger_, GMEL. S. N. 1789, 270. _Falco polyagrus_, CASS. B. Cal. & Tex. pl. xvi (dark figure).