BEYCON. — TETEAGONOPTEEUS. 169 



Hah. Guatemala, Rio Chisoy, Rio Usumacinta i ^, Rio Motagua ^ ^ and Lake Yzabal i - 

 {Godman & S'alvin). 



Six specimens, measuring up to 400 mm. in total length. 



The types of Brycon dentex, from Western Ecuador, have 18 gill-rakers on the lower 

 part of the anterior arch, 47 to 50 scales in a longitudinal series, the lower jaw shorter, 

 the eye larger and the interorbital region narrower than in B. c/uatemalensis, and the 

 body uniformly silvery. 



Gill (Proc. Ac. Philad. 1877, p. 188) has recorded B. de^itex from Lake Nicaragua, 

 but judging from Meek's description (Publ. Columbian Mus., Zool. vii. 1907, p. 109) 

 the Nicaraguan species is not Brycon dentex and may prove to be distinct from 

 B. guatemalensis. 



2. Brycon striatulus. 



Chalcinopsis striatulus, Kner, Sitzgsb. Bayer. Ak. 1863, p. 226 ' ; Giiath. Cat. Fish. v. p. 337 (1864) % 

 Chalcinopsis chagrensis , Kner, 1. c. p. 338 \ 



Depth of body 2| to 3j in the length, length of head 4| to 4|. Snout a little longer than eye, the diameter 

 of which is 4 to 4g in the length of head ; interorbital width 2^ to 2| in the length of head. Jfaxillary 

 extending nearly to below middle of eye ; lower jaw a little shorter than the upper ; prtemaxillary teeth 

 in 4 series. 13 or 14 gill-rakers on the lower part of the anterior arch. 70 to 77 scales in a longitudinal 

 series (exclusive of 4 or 5 on the basal part of the caudal), 12 to 15 between dorsal fin and lateral line, 

 8 or 9 between lateral line and root of ventral fin. Dorsal 11-12 ; origin behind the veutrals : free edge 

 nearly straight ; longest ray shorter than the head. Anal 33-39, of 3 or 4 simple and 30 to 35 branched 

 rays ; anterior part deep and convex, free edge emarginate. Pectoral nearly as long as or shorter than 

 head, sometimes reaching the ventrals, which may extend to the anal. Caudal forked. Coloration as in 

 the preceding species. 



Hal. Costarica, Juan Viiias and El Pozo del Rio Grande {Undenvood) ; Panama, 

 Rio Chagres ^ ^. 



Here described from several specimens, measuring up to 230 mm. in total length. 



5. TETRAGONOPTERUS. 



Tetragonoplerus, Cuv. Regne Anim. ii. p. 166 (1817) ; Giintli. Cat. Fish. v. p. 317 (1861) ; Jord. 

 & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 333. 

 This genus comprises a large number of species from South America and a few from 

 Mexico and Central America. 



Synofsis of the Mexican and Central- American Species. 

 I. Interorljital width 2g to 3 in the length of head; 10 to 15 gill-rakers on the lower part of 

 the anterior arch. 

 Anal 25-33 (3-4/22-29) ; maxillary extending to below anterior edge or 

 anterior part o£ eye ; diameter of eye 3 to 3i in the length of head (in 



specimens of 65 to 120 vara.) 1. ceneus. 



Aual 23-29 (3-4/20-25) ; maxillary extending to below anterior I of eye ; 

 diameter of eye 2^ to 3 in the length of head (in specimens of 65 to 

 130 mm.) 2. macrophlluiTm,us. 



BIOL, centr.-amer., Pisces, Fehriiary 1908. Z 



