Both American and European students of Tertiary Echini have, as a rule, failed to make any comparisons between species on the opposite sides of the Atlantic. Only Guppy and Cotteau1 reported some species as common to both regions, and Gregory,2 after a visit to the collections in the United States, wrote an interesting article on this subject.
In order to prepare for a more detailed investigation of the subject,3 I attempted some time ago to summarize the publications on the fossil Echini of North America and I described a few new or little known species. This was a difficult task, because the literature is scattered and much of it is not easily found in Europe. My work soon lost a part of its importance because of the appearance, four years later, of the great monograph by Clark and Twitchell, which was based on a greater wealth of material than . . .