ANNOTATED LIST OF THE SPECIES 137 
Genus 49: AGENEIOSUS Lacépéde 
Ageneiosus Lacépéde, 1805, Hist. Nat. Poiss., V, 132; 
Eigenmann, and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 299; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 397; 
Kigenmann, 1912, Mem. Carnegie Mus., V, 204. 
Hypophthalmus Schomburgk, 1849, Fish. Brit. Guiana, 191. 
Pseudageneiosus Bleeker, 1863, Nederl. Tijdsch. Dierk., I, 108. 
Ageniosus Giinther, 1864, Cat. Fish. Brit. Mus., V, 191. 
Type: Ageneiosus armatus Lacépede 
La Plata to Paranahyba, Guianas, and Peru 
Teeth villiform; barbels at mawillaries only; eyes large, lateral, and snout 
much longer than eye; dorsal fin weak, with a weak spine and 6-7 rays; adipose 
very short; anal fin very long; ventrals behind the vertical from the dorsal, the 
inner rays adnate to sides for at least half their length; no humeral process; lateral 
line zigzag, with many branches given off at the angles; occipital process united 
to the dorsal plate. 
101. AGENEIOSUS UCAYALENSIS Castelnau 
Ageneiosus ucayalensis Castelnau, 1855, Anim. Amér. Sud, Poiss., 49, pl. xvii, fig. 2, Ucayali; 
BKigenmann and Eigenmann, 1888, Proc. Cal. Acad. Sei., (2), I, 150; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 306; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 397. 
Peruvian Amazon 
15784, 4, 110-260 mm., Lago Cashiboya, Allen, August 1920. 
15785, 2, 168-200 mm., Iquitos, Allen, September, 1920. 
15911, 1, 102 mm., Pebas, Peru, Steere, specimen too Juvenile for accurate determination, probably 
belongs here. 
Our Cashiboya specimens may be described as follows: 
Head 4 in the length to the end of the middle caudal rays; greatest width, at 
pectoral basis, 1.6 in the length of the head; greatest depth, at origin of anal, 1.4 
in the head; eye 6.5 in the head, 3.4 in the interorbital space. 
Head extremely flattened and spatulate toward anterior, its dorsal and ventral 
profiles straight, its greatest depth at occiput 2.4 in the length of the head; body 
becoming extremely compressed, narrowing from its greatest width at the mid- 
pectoral level, which is equal to the interorbital space, and 1.2 in the depth at the 
same point; width of caudal peduncle 2 in its elevation; both dorsal and ventral 
profiles moderately convex. 
Mouth very wide and inferior, gape exceeding the inferior interorbital space 
and equalling that of the dorsal interorbital; eye lateral, moderate, slightly ex- 
serted on the rounded lateral angle of the head. Premaxillary broadly extended 
by a distance equal to the diameter of the eye, and, together with the mandible, 
thickly set with minute recurved teeth in a band; the mandibular band one fourth 
as wide as the length of the mandible. Inferior portion of gill membrane much 
