Should no unforeseen circumstance prevent, the Bulletins will continue to be issued at convenient irregular intervals, as material may come to hand; the strictly serial character of the publication being maintained. The actual date of issue is given on the temporary cover of each, as it is important to fix with precision the appearance of the successive numbers of a periodical in which so many new genera and species are described.
This publication, answering so fully the special purpose for which it was established, is regarded as one of the most important means to the main ends which the Survey has in view. It has already acquired a character and standing which render it favorably comparable to the regular "Proceedings" or other similar publications of any of the learned bodies of this country or Europe. Its scope includes the whole range of the subjects for the investigation of which the Survey is conducted, and the appearance of which in this connection does not in any way restrict the plan of the formal Reports of the Survey. The volumes already issued contain articles upon Archæology, Ethnography, Linguistics, Geology, Topography, Geography, Palaeontology, and Natural History in general, suitably illustrated with plates, cuts, and maps; and no effort will be spared in the future to maintain the high standard which the present volume so conspicuously illustrates.
The thanks of the Survey are due to Dr. Elliott Coues, U. S. A., his careful and able conduct of the periodical.
F. V. HAYDEN, United States Geologist.