7. S. grayi.—The “Freshwater Herring” of Lough Melvin, Ireland.
8. S. colii.—Charr of Loughs Eske and Dan.
9. S. hucho.—The “Huchen” of the Danube, growing to the size of the Salmon.
10. S. alipes from lakes in Boothia Felix and Greenland.
11. S. arcturus.—The most northern species from 82° lat.
12. S. fontinalis.—The common “Brook-trout” of the United States.
13. S. oquassa.—A lake species from the State of Maine.
Oncorhynchus differs from Salmo only in the increased number of anal rays, which are more than fourteen. All the species are migratory, ascending American and Asiatic rivers flowing into the Pacific. The Californian Salmon (O. quinnat?) belongs to this genus.
Other allied genera are Brachymystax and Luciotrutta.
Plecoglossus.—Body covered with very small scales. Cleft of the mouth wide; maxillary long. Dentition feeble; intermaxillaries with a few small, conical, pointed teeth; the teeth of the maxillaries and mandibles are broad, truncated, lamellated and serrated, movable, seated in a fold of the skin. The mandibles terminate each in a small knob, and are not jointed at the symphysis. The mucous membrane in the interior of the mouth—between the terminal halves of the mandibles—forms a peculiar organ, being raised into folds, with a pair of pouches in front and a single one behind. Tongue very small, with minute teeth, its apical part being toothless; palate apparently without teeth.