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Page:Popular Science Monthly Volume 73.djvu/121

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Glossina oligocenus Scudder 1892 PSM V73 D121.png

Fossil Tsetse Fly (Glossina oligocena). The tsetse flies are no longer found in America. (Much enlarged.)

scarcely visible at all, especially on the wet shale as it is dug out; but under a strong lens they show every detail of the structure of the wings. On the other hand, some specimens which superficially appear excellent prove upon minute examination to be of small scientific value.

When the fossils have been obtained, it is no easy matter to determine and describe them. In the case of the plants, many species are easily recognized and can be classified with much certainty; but there are living species of oaks and maples, for example, which possess foliage wholly unlike that which we usually associate with those names. A maple from Japan, judged by its leaves, would be taken for a hornbeam; some oaks resemble willows. The commonest leaf in the shales was considered by Lesquereux to be allied to the water elm of the southern states; but we have found some pieces with the fruit attached, and it seems to be a beech. Calyces, once supposed to belong to persimmon or some allied plants, prove to be those of a poplar; while the giant redwood itself was first introduced as a moss, from a fragment of a twig!

The insects, when well preserved, offer much better characters than most of the plants. Unfortunately, however, they are frequently indistinct or fragmentary, and the accurate determination of the remains becomes extremely difficult. Only those who have worked on fossil insects can appreciate at their proper value the tremendous labors of Scudder, resulting in the description and classification of many hun-