MAY, 1902. THE ICHTHYOLOGY OF MEXICO MEEK. 89 



g. Dorsal and anal fin each of less than 18 rays; body elongate, 

 not much compressed. ZOOGONETICL'S. 



gg. Dorsal and anal fins each of 19 or more rays; body com- 

 pressed. GIRARDINICHTHYS. 



bb. Outer series of teeth incisor like, bicuspid or tricuspid. 

 (Cyprinodontinae). 



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

 behind them. 



<'. Intestinal canal about \\ in total length of body; the teeth 

 very firmly attachd. CHARACODOX. 



?<'. Intestinal canal about 2 in total length of body; teeth less 

 firmly attached. CHAPALICHTHYS. 



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

 them. 



/. Dorsal fin short, of 10 to 12 rays, the first ray slender and 

 rudimentary. 



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

 stout grooved spine. JORDAXELLA. 



ccc. 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. 



k. 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. 



PSEUDOXIPHOPHORUS. 



//. Dorsal fin short, of 6 to 10 rays: anal short. GAMRUSIA. 



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

 each of 9 to ii rays. KELOXESOX. 



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

 vertical fins short, of 9 to 11 rays. AXABI.EPS. 



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 bicuspid, with villiform 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. (Goodeinae.) 



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



