Page:Popular Science Monthly Volume 10.djvu/283

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269
THE EARLIER FORMS OF LIFE.

ical analysis, so that whatever cannot be determined in the one will be ascertained by the other method.

He was accordingly gratified to recognize in one of his rock-sections the fragment of a rhizopod. The structure has some resemblance to the acaleph Chætetes, but on account of the minuteness of the layers it should be classed with the rhizopods, reminding one very much of the Stromatopora. Figs. 7 and 8 illustrate these organisms magnified thirty-five diameters, thus making the breadth of the cells only 1/280 of an inch. The smaller figure is probably a section of the

PSM V10 D283 Protozoan fossil from hanover n h.jpg
Fig. 8.—Protozoan Fossil, from Hanover, N.H.

same rhizopod, cut in a different direction. The rock holding these fossiliferous bits is diabase, a variety common between Connecticut Lake and Bellows Falls, both in New Hampshire and Vermont.

Since the naming of Stromatopora by Goldfuss fifty years since, naturalists have separated the acaleph structures from the true corals, but this genus is generally regarded as different from either of them. Prof. Hall described it as a polyp-coral in his "Paleontology of New York," but would not so regard it now. The most common form of it, as figured by him, is herewith presented (Fig. 9), from the Niagara limestone of Lockport, occurring in masses one or two feet in diameter. It is a protozoan coral, assisting in the work of reef-building, however, as much as the polyp-structures. By way of comparison we add a figure of a bryozoan mollusk (Lichenalia concentrica), from the same formation and locality with the Stromatopora (Fig. 10). The relations of our new specimens are rather with the first of these forms, and will probably be described hereafter as species of Stromatopora.

It is an interesting fact that these "layer corals" have impressed the minds of all students of the Eozoön by their resemblances to the