The specimens described are those having the breast most distinctly spotted. Specimens vary, in length of wing, from 17.50 to 20.50. There appears to be no sexual difference in size. The distinctness or identity of the European and North American Ospreys can only be determined by the comparison of a very large series; this we have not been able to do, and although it is our belief that they should not be separated, the impressions received from a close inspection of the specimens before us (twenty-seven American and eighteen European) seem to indicate the propriety of distinguishing them as races. The male of the pair described appears to be perfectly identical, in all respects except size, with a very perfect, finely mounted European male; indeed, the only discrepancy is in the size, the wing of the European bird being only nineteen inches, instead of twenty inches as in the American. The female, however, differs from European females in having the brown on the breast in the form of detached faint spots, instead of a continuous grayish-brown wash, more or less continuous. The types of our descriptions are the only specimens of the American series which show even an approach to the amount of spotting on the breast constant in birds from Europe. The American bird, as indicated by the series before us, would seem to be rather the larger; for the European specimens measure uniformly about an inch less than the American in length of the wing. In all the American specimens, of both sexes, the shafts of the tail-feathers are continuously white, while in the European they are clear white only at the roots or for the basal half. While, in consideration of the above facts, I am for the present compelled to recognize the American _Pandion_ under the distinctive name of _carolinensis_, I may say, that, if any European birds occur with the breast immaculate,—no matter what the proportion of specimens,—I shall at once waive all claims to distinctness for the American bird. LIST OF SPECIMENS EXAMINED. National Museum, 7; Philadelphia Academy, 3; New York Museum, 1 (Brazil); Boston Society, 6; Museum Cambridge, 9; Cab. G. N. Lawrence, 1; Coll. R. Ridgway, 1. Total, 28. _Measurements._ +----+-----------+-----------+---------+---------+-----------+----------+ |Sex.| Wing. | Tail. | Culmen. | Tarsus. |Middle Toe.|Specimens.| +----+-----------+-----------+---------+---------+-----------+----------+ | ♂ |19.00–20.50|10.00–10.50|1.35–0.00|2.25–2.40| 1.80–1.85| 5 | +----+-----------+-----------+---------+---------+-----------+----------+ | ♀ |18.75–19.00| 8.80–9.50|1.25–1.35|2.00–2.25| 1.70–1.80| 4 | +----+-----------+-----------+---------+---------+-----------+----------+ Second and third quills longest; first shorter or longer than fifth.