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covered, this negative evidence would have its value, as it would indicate that the physical conditions were not favorable to life, and an explanation for this fact might be found. It is scarcely necessary to mention that care should be taken not to mistake the shells occurring in modern swamp deposits associated with the ancient beaches for true lacustral fossils.

About the borders of the present lakes and sometimes even below the level of the lowest of the ancient beaches the remains of the mastodon, elephant, giant beaver, elk, bison, deer, etc., have been found. The recency of the existence of such of these animals as are extinct may thus be established, as well as the former distribution of those still living in other regions.

Evidence of the existence of man has been reported from one of the old lake ridges in New York, and it is important that this interesting discovery should be sustained by evidence from other localities. Stone implements especially should be looked for in undisturbed lacustral clays, and in the gravels of the ancient beaches.

The remains of forests have been stated to occur in the lacustral clays adjacent to the south shore of Lake Erie. It is desirable to know the extent of these deposits and how continuous they are; also the character of the plant remains they contain, and whether they have been disturbed from the position in which they grew. Some of the questions that may be asked in this connection are: Was the basin drained and forest covered before the vegetable remains were buried, or were the plants floated to their present position, or did they grow on moraines covering the stagnant border of the retreating glacier and become involved and buried in morainal material as the ice melted?

6. Life in the present lakes.—The fauna of the present lakes has a bearing on their past history, for the reason that in the deeper parts of lakes Superior and Michigan crustaceans and fishes have been found which are believed to be identical with marine forms. These may be considered as "living fossils," and are thought by some to indicate that the lakes in which they occur were formerly in direct communication with the ocean. If