52 VERTEBRATE ANIMALS OF THE UNITED STATES 



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; 

 pseudobranchias present; fins 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. 



Ci Mouth large, terminal, protractile forward i. Ictiobus. 



C2 Mouth small, inferior, protractile downward 2. Carpiodes. 



hi Scales smaller, about 56 in the lateral line 3. 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 Momatain region; hinder 



division of air bladder slender 4. Pantosteus. 



Co Hinder division of air bladder broad. 

 di No hump back of head. 



ei Mouth inferior, with thick papillose lips 5. Catostomus. 



0,1 Mouth large, terminal, with thin lips . 6. Chasmistes. 



d-i A high hump back of the head 7. Xyrauchen. 



bo Scales larger, 36 to 50 in the lateral line. 



Ci Lateral line wanting or incomplete; air bladder in 2 

 parts. 



di Lateral line entirely wanting 8. Erimyzon. 



d-i Lateral line interrupted 9. Minytrcma. 



Co Lateral line complete; air bladder in 3 parts, 

 di Lower lip entire or merely lobed. 



ei Teeth compressed; mouth small 10. Moxostonui. 



e-> Lower teeth enlarged and cylindrical; mouth 



large n. Placopharynx. 



do Lower lip split, forming two separate lobes 12. Logochila. 



I. Ictiobus Rafinesque. Buft"alo fish. Large, rather stout fishes 

 with large head, furrowed opercles and broad subopercles; fontanelle 

 present; mouth large for the family; lips thin; scales large; lateral 

 line prominent; dorsal fin long, the anterior rays being longer than 



