Here, as a part of the order Crocodilia, the phytosaurs remained till within very recent years, though there have been some mild protests against the association, especially by Marsh, Zittel, and Baur. The famous English paleontologist, Richard Owen, located the “Belodontia,” as the phytosaurs were often called, in his order Thecodontia, based chiefly upon the manner of the insertion of the teeth in sockets. But this has long since been shown to have little value in the classification of reptiles. Various authors have written about the phytosaurs in later years, notably Cope, Fraas, Huene, and Jaekel, but it was J. H. McGregor who first definitely separated the phytosaurs into a distinct order, in a careful revision of the American forms. He called the order Parasuchia, after Huxley, dividing into two suborders, the Phytosauria, after Jaeger, and the Aetosauria, a group which, for lack of a better place, had previously been classed with the Crocodilia, either as a member of the Parasuchia or as an independent suborder by Zittel (the Pseudosuchia). More recently Huene has shown that certain African reptiles from the Lower Trias had certain very definite characters entitling them to an independent position, for which he proposed the order Pelycosimia. Upon the whole, however, these characters seem to be primitive parasuchian, and the group may provisionally be placed in the order Parasuchia, as a third suborder, the Pelycosimia. The order Parasuchia, then, until we know much more about the latter two groups, may be conveniently divided into three suborders, the Phytosauria, Aetosauria or Pseudosuchia, and the Pelycosimia, all of Triassic age.