Order vii Isospondyli. 



The Isospondylous Fishes. 



Anterior vertebrae simple; opercular bones distinct; pharyngeal 

 bones not falciform; jaws well developed, the maxillary broad, always 

 distinct from premaxillary, and forming part of margin of upper jaw; 

 no barbels; gills 4; ventral fins abdominal. 



KEY TO THE FAMILIES OF ISOSPONDYLI. 



a. Adipose fin none; no lateral line; ventral sur- page 



face compressed to an edge which is armed 

 with bony serratures; stomach short, mus- 

 cular, like the gizzard of a fowl; last ray of 

 dorsal fin produced into a filament Dorosomatidce 92 



aa. Adipose fin present; lateral line present; ven- 

 tral surface rounded; stomach siphonal, not 

 gizzard-like ; last ray of dorsal fin not produced 

 into a filament Salmouidcc 95 



Family IX. Dorosoiiiatidse. 



The Gizzard Shads. 

 Body short and deep, strongly compressed, covered with thin 

 deciduous cycloid scales ; belly compressed to an edge which is armed 

 with bony serratures; head rather small, without scales; no lateral 

 line; gill membranes not united, free from the isthmus; pseudo- 

 branchia large; dorsal fin short, its last ray produced into a long fila- 

 ment; anal fin long and low: stomach short, muscular, like the 

 gizzard of a fowl. Mud-eating fishes of warm regions. 



KEY TO THE GENERA OF DOROSOMATID/E. 



a. Maxillary short, in two pieces, with a notch page 



on outer margin Dorosoma 92 



aa. Maxillary long, curved, in three pieces, and 



without a notch on its outer margin Signalosa 94 



40. Dorosoma Rafinesque. 

 The Gizzard Shads. 

 Dorosoma Rafinesque, Ichth. Ohiensis, 39, 1820. (Type, Dorosoma 



notata Rafinesque = Megalops cepedianum Le Sueur.) 

 Body short, deep, and strongly compressed; dorsal and ventral 

 outlines similar; head rather small; snout blunt, overlapping the small 



