The group of Crossopterygians, first separated as a family from the other Ganoids by Huxley, constituted a fortunate innovation, and so was its division into two minor groups, by which the existing forms (_Polypteroidei_) were separated as Cladistia. The divisions of the Actinopteri, which includes all Teleostomes other than the Dipneusti and Crossopterygii also showed, on the whole, a correct appreciation of their relationships, the Chondrostei being well separated from the other Ganoids with which they were generally associated. In the groupings of the minor divisions, which Cope termed orders, we had a decided improvement on the Cuvierian-Müllerian classification, the author having utilized many suggestions of his fellow countrymen Theodore Gill, who has done much towards a better understanding of their relationships. In the association of the Characinids with the Cyprinids (Plectospondyli) in the separation of the flat-fishes from the Ganoids, in the approximation of the Lophobranchs to the sticklebacks and of the Plectognaths to the Acanthopterygians, and in many other points, Cope was in advance of his time, and it is to be regretted that his contemporaries did not more readily take up many of his excellent suggestions for the improvement of their systems. In the subsequent period of his very active scientific life, Cope made many alterations to his system, the latest scheme published by him being the following ("Synopsis of the families of Vertebrata," _Amer. Natur._, 1889, p. 849):-- Class : Agnatha. I. Subclass : OSTRACODERMI. Orders : Arrhina, Diplorrhina. II. Subclass : MARSIPOBRANCHII. Orders : Hyperotreti, Hyperoarti. Class : Pisces. I. Subclass : HOLOCEPHALI. II. Subclass : DIPNOI. III. Subclass : ELASMOBRANCHII. Orders : Ichthyotomi, Selachii. IV. Subclass : TELEOSTOMI. (i.) Superorder : _Rhipidopterygia._ Orders : Rhipidistia, Actinistia. (ii.) Superorder : _Crossopterygia._ Orders : Placodermi, Haplistia, Taxistia, Cladistia. (iii.) Superorder : _Podopterygia_ (Chondrostei). (iv.) Superorder : _Actinopterygia._ Orders : Physostomi, Physoclysti. This classification is that followed, with many emendations, by A. S. Woodward in his epoch-making _Catalogue of Fossil Fishes_ (4 vols., London, 1889-1901), and in his most useful _Outlines of Vertebrate Paleontology_ (Cambridge, 1898), and was adopted by Günther in the 10th edition of the _Encyclopaedia Britannica_:--