FAMILY XL PCECILIID.E. 129 



ones being the larger ; teeth not movable ; scales large ; dorsal and anal 

 fins usually small, the dorsal in advance of the anal ; anal fin of male 

 much advanced, and modified into an intromittent organ which is 

 about as long as head ; alimentary canal short, usually about the length 

 of the body; branchiostegals 6; vertebrae about 32. 



This genus comprises a group of small fishes living in swamps, 

 ponds, and small streams of southern United States, Cuba, Mexico, 

 and Central America. They are viviparous and feed on insects, seeds, 

 and crustaceans. 



KEY TO THE SPECIES OF GAMBUSIA. 



a. Body with from 2 to 6 narrow, dark vertical PAGE 



bars from medial line of dorsal to or below 



axis of the body fasciata 129 



aa. Body without narrow dark vertical bars on its 



upper half. 



b. Side with a broad dark interrupted band, 

 made up of short vertical bars ; origin of dorsal 

 fin to base of caudal 2 in its distance to tip of 



snout gracilis 130 



bb. Side with a narrow dark continuous band or 



streak, 

 c. Scales in the lateral series 30 or more; head 



3/4 to 3^4 i n the body affinis 130 



cc. Scales in the lateral series 26 to 28; head 4^ 



in the body \ infans 131 



bbb. Sides without band or streak except on 



middle of caudal peduncle ; scales 8-3 2 bonita 132 



118. Gambusia fasciata sp. nov. 



Type, No. 4715, F. C. M., 2.1 inches in length; San Geronimo, 

 Oaxaca. 



Pacific slope streams of the Isthmus of Tehuantepec. (San 

 Geronimo; Tehuantepec.) 



FIG. 37. GAMBUSIA FASCIATA Meek. 



