CLASSIFICATION OF FISHES. 461 
Order 2. Branchioganoided (Polypterus). 
Order 8. Hyoganoidei (Lepidosteus, Amia). 
Subclass III. Teleostei—Skeleton bony; skull composed of numerous 
bones ; optic nerves crossing each other ; usually four pairs 
of gills, with several opercular bones; heart without a cone, 
but with ‘an arterial bulb; intestine generally without a 
spiral valve ; mostly oviparous. 
Order 1. Opisthomi (Notacanthus). 
Order 2. Apodes (Anguilla). 
Order 3. Nematognathi (Amiurus). 
Order 4. Scyphophori (Mormyrus). 
Order 5. Teleocephalt (Salmo, Perca, Gadus). 
Order 6. Pediculati (Lophius). 
Order 7. Lophobranchit (Hippocampus). 
Order 8. Plectognathi (Tetrodon, Mola), 
Laboratory Work.—Fishes should usually be dissected, except when 
large, under the water; small specimens can be pinned down to the 
bottom of cork- or wax-lined dissecting pans, and the more delicate 
parts worked out with fine scissors and knives. The brain and spinal 
cord can be dissected with ease, provided care be taken, with scalpel 
and scissors, as the bones covering them can be cut away by means of 
stout scissors and bone-pliers and fine surgical saws. Longitudinal 
sections will bring out the relations of the brain and beginnings of the 
nerves, and transverse sections of the tail may be made to show the 
disposition of the muscles. The skeleton may be prepared whole by 
removing the flesh carefully from alcoholic or partly macerated speci- 
mens, Disarticulated skeletons for study can be made by parboiling 
the fish and then separating the bones from the flesh, To study the 
circulation, careful injections should be made by the use of an inject- 
ing syringe, with wax, plaster of Paris, or vermilion as the injecting 
medium. 
Crass V.—Dipnor (Lung-fish). 
General Characters of Dipnoans.*—The lung-fishes are 
so called from the fact that, often being in pools and streams 
liable to dry up, they breathe air directly, having true lungs, 
like those of Amphibians, as well as gills. From the nature 
* Hyrtl, Lepidosiren paradoxa. Prag, 1845. 
