288 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



maxillary with a few small teeth on its edge; mandible with a single 

 series; lateral line incomplete, directed downward and backward; dorsal 

 inserted far back; pectorals large; ventrals very small; adipose present. 



35. Thoracocharax macula tus (Steindachner). Paribiba. 

 Gasteropelecus maculatus Steindachner, Denkschr. K. Ak. Wiss. Wien, 



XLI, 1879, 1 68 (Rio Mamoni, Chepo, Panama); Jordan & Ever- 



mann, Bull. U. S. Nat. Mus., XLVII, 1896, 338; Regan, Biol. 



Cent. Amer., Pisces, 1908, 173. 



Head 3. 35 to 4; depth i. 7 to 1.9; D. ioorii;A. 33 to 36; scales 3oto 35. 



Body deep, strongly compressed; the dorsal profile straight over 

 eyes, but slightly convex from nape to dorsal; the thoracic region much 

 dilated, the abdomen with a sharp keel; head small, flat above; snout 

 blunt, 3.4 to 4 in head; eye 3.1 to 4; interorbital 2.1 to 2.45; mouth small, 

 nearly vertical; lower jaw projecting; maxillary reaching anterior margin 

 of eye; premaxillary teeth in 2 series, the outer series consisting of only 

 2 conical teeth, near tip of jaw, the second series with 10 tricuspid teeth; 

 maxillary with 4 or 5 pointed teeth on its edge; lower jaw with a single 

 series, anteriorly with 8 tricuspid teeth and abruptly smaller ones at 

 sides; gill-rakers poorly developed; lateral line incomplete, directed 

 downward and backward toward about the third ray of anal, failing to 

 reach base of anal by from 3 to 6 scales; scales large along side, reduced 

 on abdomen and above base of anal, the rows directed downward and 

 backward on lower part of side; dorsal fin small, its origin notably behind 

 origin of anal, about midway between margin of preopercle and tip of 

 caudal; adipose fin small, just behind vertical from base of last anal 

 ray; caudal fin forked, the lobes subequal; anal fin rather long, its base 

 equal to depth of body at origin of dorsal; ventral fins not much longer 

 than pupil, inserted just in front of vent; pectoral fins large, reaching 

 beyond origin of anal, 2 to 2.25 in length of body. 



Color silvery, darker above; sides sometimes with a faint plumbeous 

 band; no caudal spot. Chromatophores on scales so arranged as to form 

 dotted vertical lines on sides; abdominal keel dusky. Fins unmarked. 



Of this species there are at hand nearly 300 specimens, ranging in 

 length from 42 to 92 mm. These were taken near Chorrera, Panama, 

 and in the Rio Bayano and Rio Tuyra basins. 



We have for comparison specimens of T. brevis Eigenmann, from 

 Raspadura, Atrato Basin, Colombia. This is certainly a very closely 

 related species, if in fact distinct. The two seem to intergrade, but T. 

 brevis averages fewer scales in the lateral series and the average depth is 

 slightly greater. 



Habitat: Pacific slope of Panama. 



