Biological Inductions from the Evolution of the Proboscidea 1

of the open ocean as the source of the material as in the case of the Sargasso-sea faunas. Such is the Genessee shale which like the Genundewa limestone contains in the abundant Styliolinas a typical planktonic element, the Genundewa limestone representing a Devonian pteropod-ooze. The widely extending Chatanooga shale is characterized by the conodonts, now recognized as the teeth of cyclostomes. It was formed in nearshore and lagoonal areas where the cyclostomes died after the spawning season but which were not open to Sargasso-sea invasions from the ocean. The same is true of the Carboniferous and Permian shales. It is probable that when attention is directed to the possible planktonic elements of the Paleozoic marine faunas, more forms will be recognized as being of that nature.