A SYNOPSIS OF THE KACES OF THE CRESTED TERN, THALASSEUS BERGII (LICHTENSTEIN). By Harey C. Oberholsee, Of the Biological Survey, United States Department of Agriculture. The identification of United States National Museum material collected in the East India Islands by Dr. W. L. Abbott has involved a canvass of all the races of Thalasseus hergii. Some of these have a more or less uncertain status, owing to the divergent views of recent authors;^ and the following conclusions, based upon a careful study of the questions involved, throws, I hope, a little further light on the relationships and geographical distribution of the various subspecies. Although the specimens examined have not been numerous, only about 45, they are of importance since none of them was available to either Mr. Mathews or Mr. Stresemann, the two authors who have most recently monographed the species. These specimens comprise the collections of the United States National Museuxn and the Museum of Comparative Zoology at Cambridge, Massachusetts, and include birds from most ports of the range of the species, together with the types of Sterna rectirostris Peale and Sterna hergii horeotis Bangs. While I have been unable to see examples of Thalasseus hergii thalassinus, Thalasseus hergii velox, Thalasseus hergii hakeri or Thalasseus hergii gwendolenae, the measurements of these races given by Mr. Stresemann, ^ together with notes which Mr. Mathews, who has had access to Mr. Stresemann's material, has very kindly furnished, have very well supplied the deficiency. Measurements in this paper are aU in millimeters, and those in the tables have been taken as in the author's recent paper on Butorides virescens.^ For the sake of comparison I have added the wing measurements of each race as given by Mr. Stresemann;^ since, owing to the fact that these are invariably greater than my own, there seems to be indication of a difference in our methods of measuring. • Bangs, Bull. Mus. Comp. Zoo!., vol. 36, 1901, p. 257; Mathews, Birds of Australia, vol. 2, pt. 3, Sept. 20, 1912, pp. 346-347: Stresemann, Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. » Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. » Oberholser, Proc. U. S. Nat. Mus., vol. 42, Aug. 29, 1912, p. 533. « Novit. Zool., vol. 21, Feb. 25, 1914, pp. 57-59. Proceedings U. S. National Museum, Vol. 49— No. 2121. 515
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