There is such a great amount of variability, in size, colors, and markings, that the _F. nigriceps_, Cassin, must be entirely ignored as being based upon specimens not distinguishable in any respect from typical _anatum_. Judging from the characters assigned to the _F. cassini_ by its describer (who evidently had a very small series of American specimens at his command), the latter name must also most probably fall into the list of synonymes of _anatum_. Slight as are the characters which separate the Peregrines of the New and Old World, i.e. the immaculate jugulum of the former and the streaked one of the latter, they are yet sufficiently constant to warrant their separation as geographical races of one species; along with which the _F. melanogenys_, Gould (Australia), _F. minor_, Bonap. (South Africa), _F. orientalis_, Gmel. (E. Asia), and _F. calidus_, Lath. (Southern India and East Indies), must also rank as simple geographical races of the same species. Whether the _F. calidus_ is tenable, I am unable to state, for I have not seen it; but the others appear to be all sufficiently differentiated. The _F. radama_, Verreaux (Gray’s Hand List, p. 19, No. 170), Mr. Gurney writes me, is the young female of var. _minor_. Whether the _F. peregrinator_, Sundevall (Gray’s Hand List, No. 169), is another of the regional forms of _F. communis_, or a distinct species, I am not able at present to say, not having specimens accessible to me for examination. Mr. Cassin’s type of “_nigriceps_” (13,856, ♂, July), from Chile, is before me, and upon comparison with adult males from Arctic America presents no tangible differences beyond its smaller size; the wing is a little more than half an inch, and the middle toe less than the eighth of an inch, shorter than in the smallest of the North American series,—a discrepancy slight indeed, and of little value as the sole specific character; the plumage being almost precisely similar to that of the specimen selected for the type of the description at the head of this article. In order to show the little consequence to be attached to the small size of the individual just mentioned, I would state that there is before me a young bird, received from the National Museum of Chile, and obtained in the vicinity of Santiago, which is precisely similar in plumage to the Nevada specimen described, and in size is even considerably larger, though it is but just to say that it is a female; the wing measures 13.25, instead of 12.50, and the middle toe, 2.00, instead of 1.85. No. 37,336, Tres Marias Islands, Western Mexico,—a young male in second year,—has the wing just the same length as in the smallest North American example, while in plumage it is precisely similar to 26,785, of the same age, from Jamaica. No. 4,367, from Puget’s Sound, Washington Territory,—also a young male,—has the wing of the same length as in the largest northern specimen, while the plumage is as usual.