390 Series Ostariophysi 
of carp have been formed, the “leather-carp”’ (Lederkarpfen) 
being scaleless, others, “mirror-carp”’ (Spiegelkarpfen), having 
rows of large scales only along the lateral line or the bases of 
the fins. 
Closely allied to the carp is the goldfish (Carassius auratus). 
This is also a common Chinese fish introduced in domestication 
into Europe and America. The golden-yellow color is found 
only in domesticated specimens, and is retained by artificial 
selection. The native goldfish is olivaceous in color, and where 
the species has become naturalized (as in the Potomac River, 
where it has escaped from fountains in Washington) it reverts 
to its natural greenish hue. The same change occurs in the 
rivers of Japan. The goldfish is valued solely for its bright 
colors as an ornamental fish. It has no beauty of form nor 
any interesting habits, and many of our native fishes (Percide, 
Cyprinide) far excel it in attractiveness as aquarium fishes. 
Unfortunately they are less hardy. Many varieties and mon- 
strosities of the goldfish have been produced by domestication. 
The Catostomidea.—The suckers, or Catostomide, are an off- 
shoot from the Cyprinide, differing chiefly in the structure of the 
mouth and of the lower pharyngeal bones. 
The border of the mouth above is formed 
mesially by the small premaxillaries and 
laterally by the maxillaries. The teeth of 
the lower pharyngeals are small and very 
numerous, arranged in one series like the 
teeth of acomb. The lips are usually thick 
and fleshy, and the dorsal fin is more or less 
elongate (its rays eleven to fifty in number), 
characters which distinguish the suckers from 
the American Cyprinide generally, but not 
from those of the Old World. 
About sixty species of suckers are known, 
all of them found in the rivers of North 
America except two, which have been re- yyg 392—Lower pha- 
corded on rather uncertain authority from ryngeal of Placopha- 
Siberia and China. Only two or three of ees cece ee 
the species extend their range south of the 
Tropic of Cancer into Mexico or Central America, and none 
