300 CTPUINODONTID^. 



Teeth in bands ; dorsal fin commencing before, or opposite, the origin of thtf 

 anal 8. Fundulus, p. 318. 



Teeth in hands; dorsal fin short, commencing behind the anal. Air-bladder 

 none 9. Rivulus, p. 327. 



b. Ventral fins none. 

 Teeth in bands 10. Orestias, p. 328. 



B. Sexes differentiated, the anal fin of the male being modi- 

 fied into an intromittent organ*. 



1. Teeth indsor-Wke, notched (Jenynsiina). 



Origin of the anal fin behind that of the dorsal 



11. Jenynsia, p. 331. 



2. All the teeth pointed (Anablepina). 



a. Dorsal fin long, and many-rayed. 



Teeth in bands 12. Pseudoxiphophorus, p. 332. 



b. Dorsal fin short ; eye normal. 



Snout produced 13. Belonesox, p. 333. 



Snout not produced 14. Gambusia, p. 333. 



c. Eye divided into an upper and lower portion. 

 Supraorbital arches much raised 15. Anableps, p. 337. 



II. The bones of each mandibulary are not united, the dentary 

 being moveable. Intestinal tract with numerous convolu- 

 tions. Sexes differentiated (Cypkinodontid^ limnophag^). 



1. Teeth pointed, in bands. 



Dorsal fin with not more than eleven rays ... 16. Pcecilia, p. 339. 

 Dorsal fin with twelre or more rays 17. Mollienesia, p. 347. 



2. Teeth pointed, in a single series. 



Origin of the anal behind that of the dorsal... 18. PLATTPtECiLUS, p. 350. 



Origin of the anal in advance of, rarely opposite to, that of the dorsal. 



19. GiRAEDINUS, p. 351. 



Appendix 20. Lebistes, p. 365. 



* We conclude, from the form and structure of this more or less sword-shaped 

 organ, that it is really (partially at least) introduced into the vulva of the female; 

 but it is uncertain whether it serves to conduct the milt or merely to give the 

 male a firmer hold of the female during the copulation. 



