A. ICHTHYOPSIDA.
CLASS I. PISCES.
- Order 1. Elasmobranchii.
- Suborder (1). Ichthyotomi.
- Family Pleuracanthidae. Xenacanthus.
- Suborder (2). Pleuropterygii.
- Cladoselache.
- Suborder (3). Selachii.
- Group Squalidae.
- Family Notidanidae. Heptanchus.
- Hexanchus.
- Chlamydoselache—frill-gilled shark.
- Family Cochliodontidae. Cochliodus.
- Family Cestraciontidae. Cestracion—Port Jackson shark.
- Acrodus.
- Family Scylliidae. Scyllium—spotted dogfish.
- Family Lamnidae. Odontaspis.
- Family Carcharidae. Galeus—tope.
- Family Spinacidae. Acanthias—spiny dogfish.
- Scymnus.
- Family Squatinidae. Squatina (Rhina)—angel fish.
- Group Batoidei.
- Family Pristidae. Pristis—saw-fish.
- Family Raiidae. Raia—skate.
- Family Myliobatidae. Myliobatis—eagle ray.
- Family Trygonidae. Trygon—sting ray.
- Family Torpedinidae. Torpedo—electric ray.
- Suborder (4). Acanthodii.
- Family Acanthodidae. Acanthodes.
- Family Diplacanthidae. Diplacanthus.
- Order 2. Holocephali.
- Family Chimaeridae. Chimaera—rabbit fish.
- Harriotta.
- Callorhynchus.
- Ischyodus.
- Order 3. Ganoidei.
- Suborder (1). Chondrostei.
- Family Palaeoniscidae. Palaeoniscus.
- Trissolepis.
- Family Acipenseridae. Acipenser—sturgeon.
- Scaphirhynchus.
- Family Polyodontidae. Polyodon (Spatularia)—spoon-beaked sturgeon.
- Psephurus—slender-beaked sturgeon.
- Suborder (2). Crossopterygii.
- Family Holoptychiidae. Holoptychius.
- Family Rhizodontidae. Rhizodus.
- Family Osteolepidae. Osteolepis.
- Family Polypteridae. Polypterus—bichir.
- Calamoichthys—reed-fish.
- Suborder (3). Holostei.
- Family Lepidosteidae. Lepidosteus—gar pike.
- Family Semionotidae. Lepidotus.
- Family Amiidae. Amia—bow-fin.
- Order 4. Teleostei.
- Suborder (1). Plectognathi.
- Family Balistidae. Balistes—file-fish.
- Family Gymnodontidae. Diodon—globe-fish.
- Family Ostracionidae. Ostracion—coffer-fish.
- Suborder (2). Physostomi.
- Family Siluridae.—cat-fishes.
- Family Cyprinidae. Cyprinus—carp.
- Family Esocidae. Esox—pike.
- Family Salmonidae. Salmo—salmon.
- Family Clupeidae. Clupeus—herring.
- Exocaetus—'flying fish'.
- Family Muraenidae. Anguilla—eel.
- Suborder (3). Anacanthini.
- Family Gadidae. Gadus—cod, haddock, whiting.
- Family Pleuronectidae. Solea—sole.
- Suborder (4). Pharyngognathi.
- Family Labridae. Labrus—wrasse.
- Scarus—parrot fish.
- Suborder (5). Acanthopterygii.
- Family Cataphracti. Dactylopterus—flying gurnard.
- Family Percidae. Perca—perch.
- Order 5. Dipnoi.
- Suborder (1). Sirenoidei.
- Family Dipteridae. Dipterus.
- Family Monopneumona. Ceratodus—barramunda.
- Family Dipneumona. Protopterus—African mud-fish.
- Lepidosiren.
- Suborder (2). Arthrodira.
- Family Coccosteidae. Coccosteus.
- Dinichthys.
Note. Palaeontological research has disclosed the existence of a great number of forms which seem to connect with one another almost all the orders of fishes as usually recognised. Forms connecting the living Ganoids with the Teleosteans have been especially numerous, so that these terms Ganoid and Teleostean can hardly be any longer used in a precise and scientific sense. This has rendered the subject of the classification of fishes a very difficult one. Though unsuitable for adoption in a work like the present, by far the most natural classification hitherto proposed seems to be that of Smith Woodward[15]. He considers that the course of development of fishes has followed two distinct lines, the autostylic and hyostylic (see p. 119), and groups the various forms as follows:
[a]Hyostylic.] [a]Autostylic.] Subclass 1. Elasmobranchii. Subclass 3. Holocephali. 1. Ichthyotomi. 1. (unknown). 2. Selachii. 2. Chimaeroidei. 3. Acanthodii. 3. (unknown). Subclass 2. Teleostomi. Subclass 4. Dipnoi. 1. Crossopterygii (Palaeozoic 1. Sirenoidei. and Mesozoic). 2. Crossopterygii (Cainozoic). 2. (unknown). 3. Actinopterygii. 3. Arthrodira. The primitive forms in each of these four subclasses have the fins archipterygia (see p. 127).