372 



FISHES. 



cereal ; fins without fulcra ; a long soft dorsal fin. Abdominal 

 and caudal parts of the vertebral column subequMl in extent. 

 Branchiostegals numerous. 



Amia. — Body rather elongate, sub-cylindrical, compressed be- 

 hind. Snout short, cleft of the mouth of moderate width. Jaws 



Fig. 150. — Amia oalva ; g, gular plate. 



with an outer series of closely-set pointed teeth, and with a band 

 of rasp-like teeth ; similar teeth on the vomer, palatine, and 

 pterygoid bones. Anal short ; caudal fin rounded. Gills four ; 

 air-bladder bifurcate in front, cellular, communicating with the 

 pharynx. 



The " Bow-fin " or " Mud-fish " {A. ccdva) is not uncommon 

 in many of the fresh waters of the United States ; it grows 

 to a length of two feet. Little is known about its habits ; small 

 fish, crustaceans, and aquatic insects, have been found in its 

 stomach. "Wilder has observed its respiratory actions ;^ it 

 rises to the surface, and, without emitting any air-bubble 

 whatever, opens the jaws widely, and apparently gulps in 

 a large quantity of air ; these acts of respiration are more 

 frequently performed when the water is foul or has not been 

 changed ; and there is no doubt that an exchange of oxygen 

 and carbonic acid is effected, as in the lungs of aerial 

 vertebrates. The flesh of this fish is not esteemed. 



Fossil remains occur in tertiary deposits of North America, 

 for instance in the Wyoming territory ; they have been dis- 

 tinguished as Protamia and Hypamia. 



