THE WRASSE-LIKE FISHES 2793 



wrasses. Agreeing with the wrasses in the presence of false gills and 

 f~ the cycloid scales, they differ in having four gills, and the anal fin fur- 



nished with three spines and numerous soft rays. In form, the com- 

 pressed body is either elevated or oblong, and the lateral line continuous. The sin- 

 gle dorsal fin has a spinous portion in front, and a scaly sheath along the base, 

 separated by a groove from the body scales. Small teeth are present in the jaws, 

 but the palate is toothless. Generally not exceeding a pound in weight, these 

 fishes are confined to the temperate region of the North Pacific, where they are 

 much more numerous on this than on the Asiatic side. While the majority 

 belong to the genus Ditrema, of which an example (D. argenteum} from San 

 Francisco is represented in the illustration, one species constitutes the genus Heter- 

 ocarpus, distinguished by the number of dorsal spines being from sixteen to eight- 

 een, instead of from seven to eleven. All these fishes produce living young, which 

 are contained in the sheath of the ovaries, instead of the oviduct. 



SILVERY VIVIPAROUS WRASSE. 

 (Two-fifths natural size.) 



Although some members of the preceding family may occasionally 

 enter rivers, the chromids, family Chromididcz, differ from all the other 

 fish with united lower pharyngeals in being exclusively fresh-water forms. Their 

 distribution is somewhat peculiar, and very similar to that of the lungfishes (exclu- 

 sive of the Australian form). Thus they are found in the rivers of tropical America 

 and Africa, together with Madagascar, Syria, and Palestine, one outlying genus oc- 

 curring in India; and it may be remarked that all the genera from the New World 

 are distinct from those of the Old World. Mostly of comparatively-small size, al- 

 though one species of the type genus from the Nile grows to a length of about 

 twenty inches, the chromids may be distinguished from all the other three families 

 of the present group by the absence of false gills. The body, which is somewhat 



