PTEROSALTRIA (extinct) - Diviorphodon, Ithamphorhynchus, and Pterodactylus.

As this ordinal arrangement deals in a uniform measure with extinct as well as living Reptiles, it is more complete than, and marks as great a progress in the history of herpetology as, any of the classifications recorded hitherto.

The study of fossil Reptiles had been continued after Cuvier by many workers, as Goldfuss, E. Geoffroy St Hilaire, Harlan, Mantell, G. F. Jdger, Phillips, Leidy, Falconer, Cautley, Alton, 13ronn, Kaup, Quenstedt, and especially H. von Meyer, who devoted the whole of his extra-official time to drawing with his own hand numerous trea-sures preserved in Continental collections. But none contributed more to the knowledge of fossil Reptiles than Owen himself. Indefatigable in collecting materials, and able to bring to bear upon the subject an unsurpassed knowledge ranging over the whole field of comparative anatomy, he was unrivalled in elucidating the affinities of fossil remains as well as in the production of graphic descriptions. He showed that the number of living Rep-tilian types bears but a small proportion to that of extinct forms, and, therefore, that a systematic arrangement of the entire class must be chiefly based upon dental and osteo-logical characters.

In this he was followed by HUXLEY and COPE who, however, have restricted still more the selection of classi-ficatory characters by relying for the purposes of arrange-ment on a few parts of the skeleton only. This is a matter of necessity in dealing with fossil remains, but a tendency has thereby been fostered in our times of apply_ ing the same principles in the subdivision of living Reptiles to the greater or less exclusion of the considera-tion of other parts of their organization.

Huxley and Cope attempted a further grouping of the orders which in Owen's system were merely serially enumerated as cosubordinate groups. Huxley used for Huxley , this purpose almost exclusively the position and character of the rib-articulations to the vertebral centre, the orders themselves being the same as in Owen's system : -