300 crnuxoDONTiDJi:. 



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

 anal 8. Fukdulus, p. 318. 



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

 none 9. Eivulus, p. 327. 



b. Ventral fins noiie, 

 Te«th in bands 10. Orestias, p. 328. 



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

 fied into an intromittent organ*. 



1. Teeth uicisor-lilce, notched (Jenynsiina). 



Origin of the anal fin behind that of the dorsal 



11. Jenynsia, p. 331. 



2. All tlie teeth jyohited (Anablepina). 



a. Dorsal fin long, and many -rayed. 



Teeth in bands 12. Pseudoxiphopiiorus, p. 332. 



b. Dorsal fin short ; eye normal. 



Snout produced 13. Belonesox, p. 333. 



Snout not produced 14. Gambusia, p. 333. 



0. Eye divided into an upper and lower portion. 

 Sujiraorbital 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 (Cypeinobontid^ limnophag^e). 



1. Teeth pointed, in hands. 



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

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



2. Teeth pointed, in a single series. 



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



Origin of the anal in advance of, rarely opposite to, tliat of the dorsal 



19. Giraedinus, p. 351. 



Appendix 20. Lebistes, p. 355. 



* 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. 



