What is known as the Warren mastodon was discovered in 1845, on the farm of N. Brewster, somewhere in the vicinity of Newburgh. It is an unusually complete and well-preserved skeleton, and gave occasion to the waiting of Dr. John C. Warren’s monograph entitled “Description of a skeleton of the Mastodon giganteus.” Of this work there was an edition printed in 1852, a second in 1855. The spot where this skeleton was buried is described as being situated in a small valley 300 or 400 feet in length, in which was a pond of water 30 or 40 feet in diameter. Around this the ground was wet and swampy. The summer of 1845 being unusually dry and the pond desiccated, a search was being made for marl. At a depth of about 4 feet the summit of the animal’s head was encountered. For many years this skeleton was in Cambridge, but is now the property of the American Museum of Natural History in New York. According to Warren’s description (Monograph, 1st ed., pp. 5, 211, vignette), there was a deposit of about 2 feet of bog-peat, then about a foot of peat of a reddish color. This was underlain by a bed of shell-marl of a thickness not given, but probably about 2 or 3 feet, while below this was mud changing downward into clay. Some parts of the skeleton were in this mud; but the head, the right fore-leg, the spinal column, part of the ribs, the pelvis, and the tail were embedded in the marl. However, Dr. Charles A. Lee (21st Ann. Rep. State Cabinet, New York, p. 108) affirmed that these bones were not in the marl, but were wholly embedded in the muck or peat. Dr. F. A. Lucas, of the American Museum of Natural History, New York, stated in 1902 (Science, vol. XVI, p. 169) that there is in Vassar College a skeleton of a mastodon which is supposed to have been found at Newburgh. In the collection of the Brooklyn Institute, New York, is a partial skeleton which was found in 1899 on the farm of F. W. Schaeffer, 3 miles west of Newburgh. According to Dr. J. M. Clarke (Bull. 69, N. Y. State Mus., p. 926), the bones were found lying on a stony pavement under muck and marl. Osborn (Science, vol. X, 1899, p. 539) stated that the deposit is mostly dark and contains thoroughly decomposed vegetable matter mingled with a few stones and numerous remains of trees, some of which retain marks of beavers’ teeth. The deposit appeared to consist of three layers, indicating, as supposed, the building of three distinct beaver-dams. Dr. John Mickleborough (Brooklyn Eagle, Mar. 9, 1901) stated that he had collected in this peat-swamp species of mollusks belonging to _Limnæa_, _Physa_, _Planorbis_, and _Sphærium_. He regarded it as certain that the swamp had been for a long time a fresh-water lake. Eager (op. cit., p. 73) wrote that in 1838 a mastodon tooth had been found near Newburgh, on a farm owned by Samuel Dixon. No details.