Il6 VERTEBRATE ANIMALS OF THE UNITED STATES 



C. c. borea (Girard). Head slender: upper Missouri. 



Family 5. Etheostomidae. — The darters. Body small, elongate; 

 scales ctenoid; air bladder small and often wanting; teeth all sharp, and 

 usually present on the vomer and palatines; gills 4; branchiostegals 6; 

 pyloric caeca 2 or 3; 2 dorsal fins, the anterior with many spines; anal 

 fin with 2 (rarely i) spines: about 30 genera and 100 species, all Ameri- 

 can; very small, mostly brightly colored fishes living in small clear 

 streams, largely in mountainous regions in the eastern States. 



Key to the Genera Here Included 



ai With a pig-like snout which projects beyond the mouth. ... i. Percina. 

 a2 No such snout present. 



bi Top of skull between the eyes rather flattened or depressed, 

 not strongly convex. 

 Ci Body not hyaline and extremely slender, 

 di Premaxillaries not protractile. 



Ci Belly with enlarged caducous scales, or (if 

 absent), more or less bare. 



f 1 Palatine teeth present 2. Alvordius; 



4. Serraria. 



{2 Palatine teeth absent 3. Ericosoma. 



Co Belly with ordinary scales which are never shed. . 5. Hadropterus. 



6. Swainia. 



7. Hypohomus. 

 (\i Premaxillaries proctractile. 



ei Two anal spines present. 



fi Gill membranes but shghtly connected 11. Doration. 



ii Gill membranes broadly connected across the 

 isthmus, 

 gi Belly behind the ventral fins with scales 



like the sides 10. Ulocentra. 



12. Etheostoma. 

 go Belly behind the ventral fins more or less 



scaleless 8. Cottogaster. 



9. Imostoma. 

 eo But I anal spine present. 



fi Lateral line complete 13. Boleosoma. 



I2 Lateral line incomplete 14. Vaillanlia. 



C2 Body hyaline and extremely slender and elongate. 



di Premaxillaries not protractile 15. Cryslallaria. 



da Premaxillaries protractile. 



ei But I anal spine present 17. 1'/,^//. 



en Two anal spines present 16. .1 mmocrypta. 



iS. loa. 

 b2 Top of the head between eyes not depressed but more or 

 less strongly convex; premaxillaries never protractile; 



