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had he made use of a contribution published as early as 1871, but not referred to by him. As not even a passing allusion is made to it in the previous chapter, we must retrace our steps to make good this striking omission. Edward Drinker Cope (1840-1897) was a worker of great originality and relentless energy, who, in the sixties of the last century, inspired by the doctrine of evolution, was one of the first to apply its principles to the classification of vertebrates. Equally versed in recent and fossil zoology, and endowed with a marvellous gift, or “instinct” for perceiving the relationship of animals, he has done a great deal for the advance of our knowledge of mammals, reptiles and fishes. Although often careless in the working out of details and occasionally a little too bold in his deductions, Cope occupies a high rank among the zoologists of the 19th century, and much of his work has stood the test of time.

The following was Cope’s classification, 1871 (Tr. Amer. Philos. Soc. xiv. 449).

Subclass I.  Holocephali.
  ” II.  Selachii.
  ” III.  Dipnoi.
  ” IV.  Crossopterygia, with two orders:
Haplistia and Cladistia.
  ” V.  Actinopteri.

The latter is subdivided in the following manner:—

Tribe I.: Chondrostei.
Two orders: Selachostomi and Glaniostomi.
Tribe II.: Physostomi.
Twelve orders: Ginglymodi, Halecomorphi, Nematognathi, Scyphophori, Plectospondyli, Isospondyli, Haplomi, Glanencheli, Ichthyocephali, Holostomi, Enchelycephali, Colocephali.
Tribe III.: Physoclysti.
Ten orders: Opisthomi, Percesoces, Synentognathi, Hemibranchii, Lophobranchii, Pediculati, Heterosomata, Plectognathi, Percomorphi, Pharyngognathi.

Alongside with so much that is good in this classification, there are many suggestions which cannot be regarded as improvements on the views of previous workers. Attaching too great an importance to the mode of suspension of the mandible, Cope separated the Holocephali from the Selachii and the Dipnoi from the Crossopterygii, thus obscuring the general agreement which binds these groups to each other, whilst there is an evident want of proportion in the five subclasses. The exclusion from the class Pisces of the Leptocardii, or lancelets, as first advocated by E. Haeckel, was a step in the right direction, whilst that of the Cyclostomes does not seem called for to such an authority as R. H. Traquair, with whom the writer of this review entirely concurs.

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:—

Class:  Agnatha.
I.  Subclass: Cyclostomi.
With three orders: (a) Hyperoartia (Lampreys); (b) Hyperotreti (Myxinoids); (c) Cycliae (Palaeospondylus).
II.  Subclass: Ostracodermi.
With four orders: (a) Heterostraci (Coelolepidae, Psammosteidae, Drepanaspidae, Pteraspidae); (b) Osteostraci (Cephalaspidae, Ateleaspidae, &c.); (c) Antiarchi (Asterolepidae, Pterichthys, Bothrolepis, &c.); (d) Anaspida (Birkeniidae).
Class:  Pisces.
I.  Subclass: Elasmobranchii.
With four orders: (a) Pleuropterygii (Cladoselache); (b) Ichthyotomi (Pleuracanthidae); (c) Acanthodii (Diplacanthidae, and Acanthodidae); (d) Selachii (divided from the structure of the vertebral centres into Asterospondyli and Tectospondyli).
II.  Subclass: Holocephali.
With one order: Chimaeroidei.
III.  Subclass: Dipnoi.
With two orders: (a) Sirenoidei (Lepidosiren, Ceratodus, Uronemidae, Ctenodontidae); (b) Arthrodira (Homosteus, Coccosteus, Dinichthys).
IV.  Subclass: Teleostomi.
A.  Order: Crossopterygii.
With four suborders: (1) Haplistia (Tarassius); (2) Rhipidistia (Holoptychidae, Rhizodontidae, Osteolepidae); (3) Actinistia (Coelacanthidae); (4) Cladistia (Polypterus).
B.  Order: Actinopterygii.
With about twenty suborders: (1) Chondrostei (Palaeoniscidae, Platysomidae, Chondrosteidae, Sturgeons); (2) Protospondyli (Semionotidae, Macrosemiidae, Pycnodontidae, Eugnathidae, Amiidae, Pachycormidae); (3) Aetheospondyli (Aspidorhynchidae, Lepidosteidae); (4) Isospondyli (Pholidophoridae, Osteoglossidae, Clupeidae, Leptolepidae, &c.); (5) Plectospondyli (Cyprinidae, Characinidae); (6) Nematognathi; (7) Apodes; and the other Teleosteans.

There are, however, grave objections to this system, which cannot be said to reflect the present state of our knowledge. In his masterly paper on the evolution of the Dipneusti, L. Dollo has conclusively shown that the importance of the autostyly on which the definition of the Holocephali from the Elasmobranchii or Selachii and of the Dipneusti from the Teleostomi rested, had been exaggerated, and that therefore the position assigned to these two groups in Günther’s classification of 1880 still commended itself. Recent work on Palaeospondylus, on the Ostracoderms, and on the Arthrodira, throws great doubt on the propriety of the positions given to them in the above classification, and the rank assigned to the main divisions of the Teleostomi do not commend themselves to the writer of the present article, who would divide the fishes into three subclasses:—

the characters and contents of which will be found in separate