of specific and generic differences, and the study of the habitudes of these animals. Notwithstanding, as early as 1895, I began the assemblage of materials looking specially to a revision of the New York and American eurypterid faunas. The collections of the State Museum were already pretty well supplied with representatives from the well known localities at Buffalo and in Herkimer county and now these collections have been vastly amplified, first by repeated acquisitions from the Herkimer county localities during the past 15 years, again by the close study of all outcrops of the Eurypterus beds along the line between Herkimer county and Buffalo which has progressed in connection with the field work in areal geology, then by the courtesy of the trustees of the Buffalo Society of Natural Sciences who in 1898, by special vote, placed at my disposal the extraordinary assemblage of specimens from the Buffalo cement quarries which is known, from the name of its principal contributor, as the Lewis J. Bennett Collection. Soon thereafter followed the discovery of the Eurypterus-bearing black shales at Pittsford, Monroe co., which were brought to light by the work of enlargement of the Erie canal in 1895, the species of which were described in our reports by Mr Clifton J. Sarle from material now in possession of the State Museum. To this notable addition to our knowledge has been added in years still more recent the new fauna in the dark shales of the Shawangunk grit at Otisville, Orange co., an assemblage of eurypterids remarkable for its profusion of immature growth stages; this fauna lying far to the east of all previously known occurrences of these creatures, was described in a preliminary way by the writer. Still more recently, indeed since the preparation of this book was believed to be completed, the field investigations of Dr Ruedemann have brought to light a large and new fauna in the Lower Siluric (Frankfort) shale rather widely disseminated in the lower Mohawk valley and this constitutes the very earliest assemblage of these merostomes in conditions which indicate that they formed a colony of long local duration.
The collections which have thus been brought together from the productive localities mentioned for the preparation of the present treatise have been
