646 FISHES. 



8. »S^. coin. — Charr of Loughs Eske and Dan. 



9. S. hucho. — The " Huchen " of the Danube, gro-wing to the 

 size of the Salmon. 



10. S. alipes from lakes in Boothia Felix and Greenland. 



11. S. ardurus. — The most northern species from 82° lat. 



12. S. fmtinalis. — The common " Brook - trout " of the 

 United States. 



1 3. S. oguassa. — 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 {0. quinnat?) 

 belongs to this genus. 



Other allied genera are Brachymystax and Luciotrutta. 



Plecoglosstjs. — Body covered with very small scales. Cleft 

 of the mouth wide ; maxillary long. Dentition feeble ; inter- 

 maxillaries 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 man- 

 dibles 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 pecu- 

 liar 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. 



A small aberrant form of rreshwater-Salmonoids abund- 

 antly found in Japan and the Island of Formosa. 



OsMERUS. — Body covered with scales of moderate size. Cleft 

 of the mouth wide j maxillary long, extending to, or nearly to, 

 the hind margin of the orbit. Dentition strong ; intermaxillary 

 and maxillary teeth small, much smaller than those of the man- 

 dible. Vomer with a transverse series of teeth, several of which 

 are large, fang-like ; a series of conical teeth along the palatine 

 and pterygoid bones. Tongue with very strong fang-like teeth 

 anteriorly, and with several longitudinal series of smaller ones 

 posteriorly. Pectoral fins moderately developed. Pyloric ap- 

 pendages very short, in small number ; ova small. 



