Page:The Habitat of the Eurypterida.djvu/261

Rh. We are now enabled to bring together all of the many lines which we have been following in tracing the affinities of the faunas which for other reasons were supposed to have come from the continent of Atlantica, and here, as in the case of the faunas of Appalachia, the great weight of evidence shows that the Bertie, Rondout, Manlius, Ludlow, Lanarkian, Baltic, and Old Red faunas are more closely related inter se than they are to the faunas which from the study of the petrogenesis of the formations in which they occur, were believed to have come from other continents.

. So far only a single fauna is known from the continent of Mississippia, and therefore it is not possible to institute any comparisons between the species found in that fauna and those from other faunas on the same continent, as was possible in the case of Atlantica and Appalachia; the most

that can be expected is that we shall find the Kokomo eurypterids distinct from all those which lived in rivers on other continents. As we shall see, the theoretical expectations are fully borne out by the facts.

The Eurypterid fauna of the Kokomo waterlime is distinct from any of the known North American eurypterid faunas. The material is never well preserved and the number both of species and of individuals is small. "Stylonurus (Drepanopterus) longicaudus," says Clarke and Ruedemann, "is a unique form among the American eurypterids being the sole representative thus far found on this continent of this rare and phylo-genetically interesting genus. From its Scottish allies, it is readily distinguished by its slender and elongated postabdomen and the long, clavate telson." (39, 320) Four specimens are known, two young and two mature individuals, and though they are in sufficiently good condition to enable Clarke and Ruedemann to make a restoration of the species, they do not approach the