138 FISHES OF WESTERN SOUTH AMERICA 
greater than the superior, containing the latter 1.6 times; confluent with the 
isthmus; a series of fine, deep lamellae on the throat merging into the branchio- 
stegals laterally; maxillary barbel minute, contained within the fold of the pre- 
maxillary, and reaching only half way to the extremity of the latter. 
Dorsal fin far forward, the distance of its origin from the snout 3.6 in the 
length to the end of the middle caudal rays, its spine finely serrate on the anterior 
border; pectoral strongly exserted on the lateral angle of the head, not reaching the 
broad ventrals by one third of their length, the spine with small retrorse hooks on 
the posterior border; anal very long, having 40 rays, its basis equal to the distance 
of the origin of the dorsal from the snout; adipose remote and short, slightly for- 
ward of end of anal, and nearly twice as far from the dorsal basis as from the tip 
of the middle caudal rays; caudal broad and deeply forked. 
Belly white; general ground color shades of saffron; black blotches across the 
narrow back merging into a black line at the adipose which extends along the 
bases of the rays of the upper caudal lobe; black blotches on occiput unite backward 
to form a black streamer below each side of the dorsal fin; forward a black line 
along each side of the fontanel, diverging along the bony crests to the snout, 
just within the nares. 
102. AGENEIOSUS BREVIFILIS Cuvier and Valenciennes 
Ageneiosus brevifilis Cuvier and Valenciennes, 1840, Hist. Nat. Poiss., XV, 242, Cayenne; 
Giinther, 1864, Cat. Fish. Brit. Mus., V, 192; 
Giinther, 1868, Proc. Zool. Soc. London, 229, Xeberos; 
Cope, 1878, Proc. Amer. Phil. Soc., XVII, 676, Peruvian Amazon; 
Kigenmann and EKigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 309. 
Pseudageneiosus brevifilis Bleeker, 1864, Nat. Verh. Holl. Wetensch., (2), XX, 88, pl. xvi, fig. 1. 
Ageneiosus (Pseudagenetosus) brevifilis Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, 
III, 397. 
The Guianas to the Amazons and Rio Paraguay 
15655, 3, 197-294 mm., Iquitos, Allen, September, 1920. 
15786, 1, 264 mm., Manaos, Allen, December, 1920. 
15959, 3, 188-240 mm., Iquitos, Morris, 1922. 
= , 1, 193 mm., Iquitos, J. C. Bradley, 1920. 
Morris’s specimens show the caudal obliquely truncate; back broader than 
usual. 
Genus 50: TYMPANOPLEURA Eigenmann 
Tympanopleura Eigenmann, 1912, Mem. Carnegie Mus., V, 203. 
Type: Tympanopleura piperata Eigenmann 
British Guiana and Peru 
The genus Tympanopleura differs distinctly from Ageneiosus, with which it is 
closely related. The air bladder is large and fills the abdominal cavity from side 
to side, forming the large pseudo-tympanum laterally; snout short, profile concave; 
the dorsal and pectoral spines are pungent and serrate on the posterior face. 
