2884 



THE BONY FISHES AND GANOIDS 



The extinct Jurassic spear beaks (Aspidorhynchus) constitute a 

 second family {Aspidorhynckida:} distinguished by the normal structure 

 of the vertebrae, the homocercal tail, and the production of the upper jaw; the gen- 

 eral form of the body and the arrangement of the fins being very similar to that 

 obtaining in the bony pike. 



THE BOWFIN AND ITS ALLIES SUBORDER Protospondyli 



The so-called bovvfin (Amia calva) of the fresh waters of the United States is 

 the sole existing representative of a second and larger subordinal group, differing 

 from the last by the imperfect ossification of the skeleton, the notochord being 

 either persistent throughout life, or if more or less completely replaced by vertebrae, 

 those in front of the caudal region have their bodies composed of three distinct ele- 

 ments (pleurocentra and intercentrum), which remain separate and alternating even 

 when fully developed. The lower jaw is complex, and composed of several pieces; in 



THE BOWFIN. 

 (One-fifth natural size.) 



the pectoral arch the infraclavicular plate is absent; and the pectoral fin has more 

 than three basal elements belonging to the true internal skeleton; while the tail is 

 always abbreviated heterocercal. 



Together with three extinct genera, the bowfin constitutes a family 

 (Amiida;) characterized as follows: The lower jaw has its suspending 

 arrangement directed backward, and the cleft of the mouth is wide; 

 the degree of ossification of the vertebrae is variable, although these often form com- 

 plete discs; the body is elongate or fusiform; the margins of the jaws are armed 



Existing 

 Family 



