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SPINY-FINNED GROUP. 
ductive arrangements, viviparous wrasses. Agreeing with the wrasses in the 
presence of false gills and the cycloid scales, they differ in having four gills, and 
the anal fin furnished with three spines and numerous soft rays. In form, the 
compressed body is either elevated or oblong, and the lateral line continuous. The 
single 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 the American 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 
Heterocarpus, distinguished by the number of dorsal spines being from sixteen to 
eighteen, instead of only from seven to eleven. All these fish produce living 
young, which are contained in the sheath of the ovaries, instead of in the oviduct. 
TRISTRAM’S CHROMID. 
chromids Although some members of the preceding family may occasionally 
enter rivers, the chromids, family Chromididce, 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 lung-fishes 
(exclusive 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 occurring 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, although 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 variable in form, is generally covered with ctenoid scales, although in 
some cases these may be cycloid; and the lateral line is more or less interrupted. 
