McGregor was quite right in retaining for the suborder the name Phytosauria, suggested by Jaeger in 1828, inappropriate as the word is etymologically, but was hardly justified in substituting the generic name _Phytosaurus_ for the long and well-known _Belodon_, because it is quite impossible to say that Jaeger’s very fragmentary specimen upon which he based the genus _Phytosaurus_ really is the same as _Belodon_. Professor Fraas very kindly showed the writer the original type-specimen of Jaeger, now preserved in the Stuttgart Museum, and both are agreed that it is impossible to prove the identity of _Belodon_ and _Phytosaurus_ from the very fragmentary and imperfect specimen. It is quite as probable, for instance, that _Phytosaurus_ and _Mystriosuchus_ are identical as that _Phytosaurus_ and _Belodon_ are. Unfortunately, this is not the only case in vertebrate paleontology where the fragmentary specimens to which names have been given are inadequate to determine the species, or genus, or even the family to which they belong; there have been very many such instances. The pioneers in paleontology were often justified in naming small and obscure fragments of bones, or single bones. One would be justified even yet in giving a name to an indeterminable fragment of a bird bone from the Triassic formation, because the discovery of a bird of any kind in that formation would be very important for science, even if its precise kind might never be recognized from the specimen. Nevertheless, the custom is a very reprehensible one when indiscriminately followed. For these reasons the writer disagrees with McGregor in substituting the inappropriate name _Phytosaurus_ for _Belodon_, the name by which the most typical forms were so long known. The Aetosauria, which have long been known from a marvelous specimen found in Würtemberg many years ago and described by the elder Fraas, need not detain us long. They were relatively small reptiles about two feet long, almost completely incased in a bony armor, and purely terrestrial in habit. The skull even yet is not perfectly known, and it is possible that when it is the group may have to be dissociated from the phytosaurs. The nostrils were not posterior, and the skull is short. Other specimens of the same group have been described from the Upper Triassic rocks of Massachusetts. The Pelycosimia of Huene are very interesting as showing apparently primitive forms with which the true phytosaurs may have been intimately related ancestrally. They, too, have a rather short skull with the nostrils in front, and were not at all aquatic in habit. Not much is known about the single genus that is located in the group, aside from the skull and a few limb bones. PHYTOSAURIA