May, igo2. Thk Ichthvoi.ogv of Mexico — Meek. 8g 



,i^-. Dorsal and anal fin each of less than i8 rays; body elongate, 

 not much compressed. zoogonkticus. 



^\^. Dorsal and anal fins each of ig or more rays; body com- 

 pressed. f;i RA R I )I \ ICHTH vs. 



/>/>. Outer series of teeth incisor like, bicuspid or tricuspid. 

 (Cyprinodontinae). 



//. Outer series of teeth bicuspid with a band of villiform teeth 

 behind them. 



7'. Intestinal canal about i| in total length of body: the teeth 

 very firmly attachd. characouon. 



Z'v. Intestinal canal about 2 in total length of body; teeth less 

 firmly attached. chapalichthvs. 



////. Outer series of teeth tricuspid, no villiform teeth behind 

 them. 



/. Dorsal fin short, of 10 to 12 ra}"s, the first ray slender and 

 rudimentary. 



//. Dorsal fin long, of 16 to 18 rays, the first developed as a 

 stout grooved spine. jordanella. 



ccr. Anal fin of the males placed well forward and modified into 

 a sword shaped intromittent organ; teeth all pointed, arranged in 

 bands. Species viviparous, the young of large size at birth. ( Gam- 

 businae. ) 



J. Eye normal, the pupil not divided by a partition; dorsal fin 

 inserted more or less behind the front of the anal. 



X'. Jaws not produced into a beak; lower jaw prominent, longer 

 than the upper. The male much smaller than the female. 



/. Dorsal fin long, of 14 to 16 rays, anal short. 



I'SEUDOXIPHOI'HORUS. 



//. Dorsal fin short, of 6 to 10 rays;. anal short. (;ami!usia. 



/'/'. Jaws produced into a moderate beak; dorsal and anal short, 

 each of g to 11 rays. heeonesox. 



jj. Eye divided into two portions by a horizontal cross partition; 

 vertical fins short, of g to 11 rays. anahleps. 



aa. Intestinal canal elongate, usually coiled on ventral and right 

 side, with numerous convolutions: dentary bones loosely joined: teeth 

 movable. Species chiefly mud eating. 



/;/. Outer series of teeth bicusjiid, with \illiform teeth, behind 

 them; anal fin of the male with first five or six rays of anal fin short 

 and stiff and separated from the rest of the fin by a notch. Species 

 viviparous, the young of large size when born. (Goodeina'.) 



n. Body robust, oblong, depth 3 to 4 in length of body; gill- 



