eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 483 



c. Preopercle entire. 



d. Gill-rakers minute; scales of the lateral line of the same size as those above or below it. 

 e. Upper gill-arch without a downward projecting lobe. 



/. Mouth large, freely protractile; end of maxillary exposed Acaropsis. 



ff. Mouth small, not greatly protractile; end of maxillary concealed. 



g. Lateral line running close to the dorsal; head densely scaled Nannacara. 



gg. Lateral line well separated from the dorsal. 



//. Anal spines three; soft fins naked, or with scales at the bases only. 



.fljquidens. 



Iili. Anal spines more than three. 



i. Ventrals inserted behind the origin of the dorsal Cichlasoma. 



ii. Ventrals inserted in front of the origin of the dorsal Mesonauta. 



ee. Upper gill-arch with a downward projecting lobe. 



j. Lateral line well separated from the dorsal for most of its length. 



k. Gill-rakers at the base of the lobe; mouth small, not greatly protractile; caudal 



emarginate Acarichthys. 



kk. Gill-rakers running at the edge of the lobe of the first gill-arch; mouth small; 



premaxillary not greatly protractile. 



/. Preorbital little if any wider than the eye; eye a little nearer to gill-opening 



than to snout; lateral line not continued on the caudal.. .Biotodoma. 



//. Preorbital twice as wide as the eye in the adult. Eye three times as far 



from the snout as from the gill-opening; lateral line forked at the caudal 



peduncle. Lower lip with a frenum Geophagus. 



jj. Lateral line running within a scale, or a scale and a half, from the dorsal. 



Heterogramma. 



del. Gill-rakers large, stiff; perciform, mouth large; scales of the lateral line larger than the rest. 



• Cichla. 



cc. Preopercle finely serrate. 



m. Jaws equal; mouth small; scales 26-29, those of the lateral line of the same size as those above 



or below it Crenicara. 



mm. Lower jaw projecting; scales of the lateral line larger than those above or below it. 



n. None of the teeth depressible; scales 55-70 Batrachops. 



nn. Inner teeth depressible; scales 38-130 Crenicichla. 



aa. First dorsal and anal rays prolonged; body much compressed, deep; gill-rakers moderate.. .Pterophyllum. 



Ch^etobranchus Heckel. 

 Chcetobranchus Heckel, Ann. Wiener Mus., II, 1S40, 401 (flavescens, brunneus). — 



Gunther, Catalogue, IV, 1862, 309 (flavescens). 



Type, Chcetobranchus flavescens Heckel. 



This genus is readily distinguished from all other Guiana Cichlids by the 

 numerous, long, setiform gill-rakers. 



327. Chaetobranchus flavescens (Heckel). 

 Chactobranchus flavescens Heckel, Ann. Wiener Mus., II, 1840, 402 (Guapore; Rio 

 Negro). — Muller and Troschel, in Schomburgk, Reisen, III, 1848, 625 



