Nearly all the mastodons are found in swamps, showing that possibly these morasses appeared to be veritable traps that hastened the extinction of these monarchs of the forest. This may be considered the popular theory of one method by which mastodons were destroyed: but there is no better authority than Professor James Hall, the present geologist in chief of the State of New York; and his opinions are entirely different. His views are, that the extinction of the mastodon was hastened by the glacial period, and that most of the remains discovered have been dropped in hollows or ponds, from the ice perhaps, and the peat formed over them. He advances in favor of this the fact that several tusks have been discovered which show evidences of glacial action. There is such a tusk in the collection of the Philadelphia Academy of Sciences, worn by supposed glacial action; and Rutgers College has the extremity of a tusk, showing what is considered by Professor Hall to be glacial striæ. Referring to the Big Bone Lick, Professor Hall says, “With our present knowledge, it would appear that this accumulation of bones, teeth, and tusks of mastodon, in Kentucky, may have been caused by the melting of a glacier in which they had become embedded, and, being gradually pushed forward to its southern limit, had been deposited in this place. There are other similar localities of less importance and extent, where mastodon remains have been obtained in considerable numbers; and it is not improbable that a critical examination of all known collections may furnish some further evidence of conditions similar to those indicated by the specimens in the Museums of the Philadelphia Academy of Sciences and of Rutgers College. “However heterodox these views may appear, as opposed to the generally received opinions of the age and relations of the mastodon, I feel quite sure that some other hypothesis than the one usually entertained must be adopted in order to arrive at a satisfactory explanation of the mode and conditions of distribution and inhumation of the mastodon and fossil elephant remains of this country.