268 Field Museum of Natural History — Zoology, Vol. X. 



KEY TO THE GENERA. 



a. Caudal fin forked; adipose fin present (except in Phanagoniates) . 



b. Scales cycloid. 



c. Teeth wanting. {CurimatincB) Curimatus, p. 269. 

 CO. Teeth in lower jaw wanting. {ParodontincB) Apareiodon, p. 270. 

 ccc. Teeth present in both jaws. 



d. Teeth in a single series in each jaw; lateral line incomplete. 

 (Chetrodontince) 



e. Adipose fin wanting; anal fin long, with more than 40 rays. 



Phanagoniates, p. 272. 

 ee. Adipose fin present; anal fin short, with fewer than 30 rays. 



f . Lower half of base of caudal in the male with a peculiar lobe of 

 enlarged scales. Compsura, p. 273. 



ff . No enlarged scales on base of caudal. 



Pseudocheirodon gen. nov., p. 275. 

 dd. Teeth in upper jaw in 2 series, those in lower jaw in a single 

 series. (TetragonopterincB) 



g. The thoracic region not greatly dilated or compressed. 

 h. Lateral line complete 



i. Dorsal fin inserted far back, its origin nearer caudal than eye, 

 notably behind origin of anal. Gephyrocharax, p. 277. 



ii. Dorsal fin inserted over or in advance of anal. 



j. Maxillary with few or no teeth; caudal spot if present not 

 extended on middle caudal rays. 



k. Second suborbital narrow, leaving a naked triangular area below 

 suture between the first and second suborbitals; first series of 

 premaxillary teeth regularly placed. Astyanax, p. 279. 



kk. Second suborbital expanded, covering nearly the entire cheek, 

 not leaving a naked triangle below suture between the first and 

 second suborbitals; first series of premaxillary teeth more or 

 less irregularly placed. Bryconamericus , p. 282. 



jj. Maxillary in adult with from 5 to 25 teeth; the inner caudal rays 

 black. Hemibrycon, p. 285. 



hh. Lateral line incomplete; no caudal spot. 



Hyphessobrycon, p. 286. 



gg. The thoracic region greatly compressed, dialated, forming a 

 semicircular disc. {GasteropelecincB) Thoracocharax, p. 287. 



ddd. Premaxillary teeth in 3 series; teeth in mandible in i or 2 series, 

 if with 2 series, the outer one composed of only 2 teeth on edge 

 of jaw and directed forward. 



I. Anal fin short, with not more than 17 rays; body long, Httle 

 compressed. {TetragonoptrincB) Creagruius, p. 289. 



