(_l_) The _dorsal vertebræ_, as well as those of the other series, present a primitive character (fig. 8) in the persistence of the notochord (540). Among the Branchiosauria the notochord was not at all or but slightly constricted intravertebrally, but among the Microsauria it was constricted so far that the notochordal remnants in each centrum resemble an hour-glass. The structure of the vertebræ among American forms agrees fully with that outlined by Credner, Fritsch, and others for the European species. The details of structure are so fully given by Zittel (642, pp. 346-353) and by Schwarz (540, 541) that it will not be necessary to state more here as to their structure, since there is nothing new to add concerning the American species. The temnospondylous vertebra of the same nature and type as exhibited by the Permian forms has its representatives (94, 478) in the Coal Measures. _Spondylerpeton spinatum_ Moodie (478) (plate 4, figs. 1, 2) and _Eryops_ sp. (plate 18, fig. 2) indicate the embolomerous and rachitomous types of vertebral structure. The occurrence of these widely different types of vertebral structure indicates a long history for the group prior to the Coal Measures. This history is further indicated by footprints in the Mississippian and Devonian of this continent. [Illustration: Fig. 8.--Vertebræ and ribs of Amphibia from the Coal Measures of Linton, Ohio. Originals in Geol. Inst. Berlin. (All after Schwarz.) A. Caudal vertebra of _Œstocephalus remex_ Cope. Lateral view. × 4. B. Caudal vertebra of _Ptyonius vinchellianus_ (?) Cope. Lateral view. × 6. C. Dorsal vertebra of _Ptyonius pectinatus_ Cope. Lateral view. × 9. D. Notochordal cones and spinal canal of _Thyrsidium fasciculare_ Cope. × 3. E. Rib of Molgophis sp. Cope. × 1.75. _c_=capitulum; _t_=tuberculum. F. Vertebra of _Molgophis_ sp. Cope, from ventral side. × 2. G. Dorsal vertebra of _Ptyonius pectinatus_ Cope. From above. × 8. H. Dorsal vertebra of _Thyrsidium fasciculare_ Cope, from below. × 2.5. I. Vertebra of _Phlegethontia linearis_ Cope, from above. × 5.5 J. Rib of _Œstocephalus remex_ Cope, from posterior dorsal region. × 5. K. Dorsal vertebra of _Thyrsidium fasciculare_ Cope, from above. × 1.5 L. Anterior dorsal vertebra (cervical?) of _Thyrsidium fasciculare_ Cope. Lateral view. × 1.5. M. Vertebra of _Phlegethontia linearis_ Cope, from side. × 5. ]