50 IMi". C. T. Ivogan on the South- American 



upper part of the anterior ])raneliial areh bearing a eom- 

 prossed lobe, Avith (lie ijill-rakers at its base. A single 

 dorsal fin, with XVI 11 rays. Anal with III G-7 rays. 

 IVctoral asymmetrical. Caudal rounded or truncate. 

 A single species from the Araguay. 



Retroculus lapidifer. 



Chromyx lapidifera, CR?^te\n. Anim. Am. Slid, Poiss. p. 16, pi. xii. fig. 1 

 (18o5) ; iSteind. Sitzb. .W. Wien. Ixxi. 187o, p. 122. ^ 



lietrocutm Boiilc»f/eri, lOiireum. & IJrav, Aim. Ac. N. York, vii. 1804, 

 p. 014 ; Tellpirr. Mi^m. Soc. Zool. Fiance, xvi. 190:3, p. 181 (1904). 



Geophagus lapidifera, Pellegr. t. c. p. 199. 



Depth of body 3 in the length, length of head 2|-3. 

 Snout long, the eye situated in the posterior half of the 

 head. Diameter of eye 4-5 in the length of head, depth of 

 ])ra.H)rbital about 2^. Maxillary extending to below the 

 nostril ; cheek with 4-6 series of scales. First branchial 

 arch with 29 gill-rakers in the outer series, 15 at the base of 

 the lobe and 14 on the lower part of the areh ; gill-rakers of 

 the inner series 21, 5 at the base of the lobe, 16 on the lower 

 part of the arch. Scales 38-39 %'• Dorsal XVI 11, the 

 soft fin scaly at the base. Anal III 6-7. Pectoral shorter 

 than the head. Caudal truncate or rounded, covered with 

 little scales. Caudal peduncle as long as deej). Yellowish, 

 with darker cross-bars ; a blackish spot at the base of the 

 anterior rays of the soft dorsal. 



R. Araguay. 



The type measures 190 mm. in total length. 



Geophagus. 



GeopJun/us, Ilec-k. Ann. Mu3. Wien, ii. 18J0, p. 383 ; Giintli. Cat. 



Fish." iv. p. 315 (1802) ; Steind. Sitzb. Ak. Wien, Ixxi. 1875, p. 107 ; 



Eifrenm. & Brav, Ann. Ac. X.York, vii. 1894, p. 621; Pellegr. 



Wem. Soc. Zool.'France, xvi. 1903, p. 188 (1904). 

 Mesops (part.), Giinth. t. c. p. 311 ; Eigeniu. & Bray, /. c. 

 Siitatioperca, ulinlh. t. c. p. 313. 

 Biotodoma (part.), Eigenru. & Kennedy, Proc. Ac. Philad. 1903, p. 533. 



Body deep or moderately elongate, compressed ; scales 

 ctenoid, large. Two lateral lines, the upper well separated 

 from the spinous dorsal. Mouth moderate ; jaws equal 

 anteriorly ; maxillary completely sheathed by the prseorbital ; 

 teeth conical, in bands ; no canines ; upper surface of head 

 to between the orbits, and opercular bones scaly ; cheeks 

 usually scaly ; prseoperculum entire. Gill-rakers short, in 

 small or moderate number (6 to 21 on the low^er jiart of the 

 anterior arch) ; upper part of anterior branchial arch bearing 



