lOO VERTEBRATE ANIMALS OE THE UNITED STATES 



Family 3. Poeciliidae. — Killifish. Small fish with moderately 

 elongate body, flattened head and rather large cycloid scales; head more 

 or less scaly; mouth small, terminal, with a projecting lower jaw; upper 

 jaw very protractile, its margin formed by the premaxillaries; branchi- 

 ostegals 4 to 6; tail not forked; no pyloric caeca; no lateral line; many 

 species ovoviviparous : about 30 genera and 180 species, occurring in 

 fresh and brackish water in all the warmer waters of Europe, Asia, 

 Africa and America; about 30 fresh water species in the United States, 

 largely in coastwise inlets and swamps of the southern States. 



Key to the Fresh Water Genera of Poeciliidae in the United States 



ai Lower jaw usually projecting beyond the upper; teeth little 

 movable; species mostly carnivorous, 

 bi Anal iin of male of normal shape; species oviparous. 



Ci Teeth pointed, not compressed, and neither bicuspid 

 nor tricuspid. 



di Teeth in more than one series i. Fundulus. 



do Teeth in a single series; dorsal fin in front of 



the anal 2. Lucania. 



C2 Teeth not pointed but notched and tricuspid. 



di Dorsal fin with lo to 12 rays 3. Cyprinodon. 



d2 Dorsal fin with 15 to 18 rays 4. Jordanella. 



hi Anal fin of male a long sword-shaped organ; species vivipar- 

 ous 5. Gambusia. 



3.2 Lower jaw short; teeth movable; species mostly mud-eating. 



bi Teeth in a single series 6. Heterandria. 



hz Teeth in more than one series 7. Mollienisia. 



I. Fundulus Lacepede. KilHfish. Body rather elongate, some- 

 times chubby; compressed behind; eyes large; teeth in 2 or more series in 

 each jaw, and pointed; air bladder present: many species, mostly Ameri- 

 can, living in fresh water and arms of the sea; about 20 species in the 

 United States. 



Key to the United States Species of Fundulus 



ai Dorsal fin with 11 to 17 rays; not top-swimming species. 



bi Dorsal fin inserted before the front of the anal; branchiostegals 

 5 or 6. 



Ci Scales 35 in longitudinal series F. hclcroclitus. 



C2 Scales 45 to 60. 



di Scales 45 F- diaphanus. 



d2 Scales 60 F. zebrinus. 



6.3 Scales 52. F. seminolis. 



b2 Dorsal fin inserted over or slightly behind the front of the 

 anal fin. 



