I have received Part ten of your GUIDE TO THE STUDY OF INSECTS, which brings the whole work so successfully to its completion. After all the good things that have been said of it at home and abroad, any commendation of mine would be quite superfluous. I will, however, express my obligation for both the pleasure and instruction I have received in reading it.--_Extract from letter of Prof. T. Wyman._ The first two parts are, we do not hesitate to affirm, the best things of the kind that our language possesses. We have seldom fallen on so thoroughly good a scientific treatise as the one whose features we have briefly sketched, and we can only conclude our notice of it by advising all our natural history readers to make its acquaintance. There is no work we should prefer to it as a book for the student, for it is a treatise which displays an absolute avoidance of mere compilation, and it is pervaded by such a tone of earnestness, and contains so many original observations, that the reader is inducted by it out of the usual book-land of idealism into the substantial region of actuality and fact.--_Scientific Opinion_, London. Too often do we meet with a manual in which there is little more than a description of the external characters which nobody is satisfied with, because it is not full enough for the mere collector, and for the general reader is too dry. Packard's work has succeeded throughout in satisfying. * * * * * THE MAMMOTH CAVE AND ITS INHABITANTS, _Or Descriptions of the Fishes, Insects and Crustaceans_ found in the Cave; with figures of the various species, and an account of allied forms, comprising notes upon their Structure, Development and Habits; with remarks upon subterranean life in general. By A. S. PACKARD, Jr., and F. W. PUTNAM. 8vo, 62 pages, 2 steel plates and 14 woodcuts, full cloth binding and appropriate stamp in gold on each side. Price $1.25 a Copy. * * * * * INSECT PINS AND CORK FOR INSECT BOXES. _Size of cork, 12x3-1/2 inches. Price, $2.00 for twelve pieces. Postage 6 cents. Large orders sent by Express._ INSECT PINS, 30 cents a hundred, $2.50 a thousand. Forceps for pinning insects, $1.35. * * * * * RECORD OF AMERICAN ENTOMOLOGY. _Edited by A. S. PACKARD, Jr._ A Year Book of Progress in American Entomology for 1868, 1869, 1870, 1871, 1872. Price of Parts for 1868 and 1869, 75 cents each. For 1870-72, 50 cents each; or the five to one address for $2.50. * * * * * IN PRESS.--"CHECK LIST OF THE COLEOPTERA OF NORTH AMERICA," prepared by Mr. G. R. Crotch. This will make an 8vo pamphlet of about 150 pages; nearly 100 pages are already printed. Address the Agency for further information. * * * * * A LARGE Number of Works on Entomological Subjects are for Sale at the NATURALISTS' AGENCY. Send for a list. * * * * *