FISHES 51 



out spines; ventral tins abdominal; no adipose lin; lower pharyngeals 

 falciform, parallel with the gill-arches; maxillaries perfect; jaws tooth- 

 less; no pyloric caeca; air bladder with pneumatic duct: 2 very large 

 families of fresh water fishes. 



Key to Families of Eventognathi 



ai Lips usually thick and flesh}'; dorsal ftn with more 



than ID rays i. Catostomidce. 



&2 Lips thin; dorsal fin with less than 10 rays 2. Cyprinidce. 



Family i. Catostomidae. — Suckers; mullets. Fishes of medium 

 size, with an elongate, more or less compressed body covered with 

 cycloid scales; head naked, without barbels; jaws toothless; mouth 

 usually with thick, fleshy, protractile lips; sides of the upper jaw 

 formed by the maxillaries; lower pharyngeal bones with a single 

 row of teeth; branchiostegals 3; gill membranes united to the isthmus; 

 pseudobranchiae present; iins not scaled; dorsal fin often long; anal 

 fin short; tail forked; air bladder large, divided into 2 or 3 compart- 

 ments: about 15 genera and 70 species, of which 2 occur in eastern 

 Asia and the others in the fresh waters of North America. They 

 live near the bottom and feed on vegetation and small, inactive animals. 

 In the spring they usually ascend the streams to spawn, often in 

 swarms. The flesh of most species is not highly valued for food. 



Key to the Genera of Catostomidae 



ai Dorsal fin long, with 24 to 30 rays; air bladder in 2 parts. 

 bi Scales large, 35 to 41 being in the lateral line. 



1. Ictiobus. 



2. Megastomatohus. 



3. Carpiodes. 

 hi Scales smaller, about 56 in the lateral line 4. Cycleptus. 



a2 Dorsal fin with 9 to 18 rays. 



bi Scales small, 50 or more in the lateral line; air bladder in 

 2 parts. 

 Ci Small species in the Rocky Mountain region; hinder 



division of air bladder slender 5. Panlosteus. 



C2 Hinder division of air bladder broad, 

 di No hump back of head. 



Ci Mouth inferior, with thick papillose lips. 



fi Scales small (over 55) 6. Catostomus. 



{2 Scales larger (under 50^. 



gi Head concave above 7. Hypentelium. 



g2 Head not concave above g. Thobiirnia. 



ti Mouth large, terminal, with thin lips 8. Cliasmistes. 



d^ A high hump back of the head 10. Xyrauchen. 



