Order vii. Isospondyli. 



THE ISOSPONDYLOUS FISHES. 



Anterior vertebrae simple; opercular bones distinct; ^haryngeal 

 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 Dorosomatida 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 Salmonidcc 95 



Family IX. DorosomatidaB. 



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 9 2 



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



without a notch on its outer margin Signalosa 94 



4O. Dorosoma Rafinesque. 

 THE GIZZARD SHADS. 



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



noiata Rafinesque = Megalops cepedianum Le Sueur.) 

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

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



92 



