ORDER CYCLOGANOIDEA 37 



Order CYCLOGANOIDEA 



Skeleton bony; vertebrse amphicoelous, as usual among fishes, the an- 

 terior ones not modified; fins without spines; ventrals abdominal; a meso- 

 coracoid; opercular skeleton complete; maxillary bordering mouth, not 

 transversely segmented; air-bladder cellular, lung-like, opening into oesoph- 

 agus. Fresh-water fishes of the United States and Canada. A single 

 living genus and family. 



Family AMIID/ZE 

 the bowfins 



Oblong, subcylindrical fishes, compressed posteriorly, and with the head 

 bluntish and its external bones corrugated and very hard, scarcely covered 

 by skin; body covered with cycloid scales; skeleton bony; fins without spines 

 or fulcra; dorsal fin long and low; tail slightly heterocercal; gills 4, a slit 

 behind the fourth; no spiracles; no pseudobranch and no opercular gill; 

 branchiostegals 10 to 12; opercular skeleton complete; throat with two 

 peculiar comb-like appendages of uncertain function; nostrils double, the 

 anterior with a short barbel; lateral line developed; optic nerves forming a 

 chiasma; jaws equal, the lower U-shaped, with a bony gular plate between 

 the rami; premaxillary not protractile; jaws and palatines with strong conical 

 teeth; vomer and pterygoids with bands of small teeth; stomach with blind 

 sac; no pyloric caeca; intestine with a rudimentary spiral valve; air-bladder 

 cellular, bifid in front, lung-like, connected by a glottis with the pharynx, 

 and capable of assisting in respiration. 



These fishes are remarkable for the simultaneous occurrence 

 of primitive ganoid characters — the cellular air-bladder, spiral 

 valve, gular plate, etc. — along with marked features of resem- 

 blance to the modern isospondylous forms (herring and their 

 allies). The species next described is the sole surviving rep- 

 resentative of a once large family, chiefly represented to-day 

 by numerous fossils. The Amiidce first appeared in the Upper 

 Jurassic of France and Bavaria (genus Megalurus), and fossil- 

 ized remains of Amia occur in the Eocene of northern Europe 

 and North America. The latter genus apparently became 

 extinct in Europe at the close of the Lower Miocene. 



