Page:The Habitat of the Eurypterida.djvu/15



From all over the world there have been recorded fourteen genera and between 150 and 160 species of eurypterids. Of these considerably more than half occur in the Siluric, about a third occurring in the Upper Siluric alone. No remains have been found in beds higher than the Permic, and until 1882 it was supposed that there were none below the Siluric. In that year Walcott discovered a few fragments in the Utica shale, of Upper Ordovicic age, and an even more remarkable fauna in the Pre-Cambric Belt Terrane of Montana. In 1901 Beecher discovered an almost perfect eurypterid in the Upper Cambric of Missouri. These discoveries, together with several more recent ones from the Ordovicic, show that the Eurypterida ranged from the Pre-Cambric through the Permic, reaching their acme in numbers, development and diversity of types in the Upper Siluric. In the following review of the occurrence North America alone will be considered first and then the rest of the world. Until the Monograph on the Eurypterida of New York appeared there was no one book containing all the information about the North American species, and it was necessary for one in quest of such knowledge to search laboriously through state reports and numerous periodicals. Now all the data have been systematically brought together and greatly added to, so that it will be unnecessary to dwell at great length upon the American formations. For the rest of the world, unfortunately, there is no one book to which the student may be referred, so that one is compelled to consult the literature of each country in each continent thus gradually bringing together the work that has been done. Because the foreign periodicals and books now out of print are inaccessible to many, a more detailed account will be given of the distribution, and the nature and correlation of the formations in other countries than is required for America.

. The earliest representative of the eurypterids is Beltina danai discovered by Walcott in the Greyson shales in the