GO Mr. C. T. Reg-an on the South- American 



Anal III 8. Dorsal and anal fins scalcless. Pectoral as 

 long as the head, extending to above the vent. Caudal 

 peduncle a little longer than deep. Olivaceous ; a dark spot 

 on the middle of the side ; an ocellus on the upper part of 

 the base of caudal ; dorsal m ith alternate light and dark 

 stripes. 



R. Amazon. 



The tyi)ical example measures 290 mm. in total length. 



12. Geophagus acuticeps. 



Geophaqua acuticeps, Ileck. Ann. Mu-s. Wieii, ii. 1840, p. 394 ; Pellegr. 



M(5iii'. Soc. Zool. France, xvi. 1903, p. 191 (1904). 

 Satatioperca acuticeps, Giintli. Cat. Fish. iv. p. 312 (18(^)2). 

 Geoph'it/us (Satanoperca) acuticeps, Steiud. Sitzb. Ak. Wien, Ixxi. 1875, 



p. u'r. 



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

 Snout 2;\-2s iu the length of head, diameter of eye Sj-Sf, 

 interorbital width 3-'^\, depth of jjrteorbital 3-3g. Max- 

 illary not extending to below the eye; jaws equal anteriorly; 

 fold of the lower lip continuous ; cheek with 5-7 series of 

 scales; 19-21 gill-rakers on the lower part of anterior arch. 

 Scales 30-31 y_"^^, 2 or 2i between lateral line and anterior 

 ravs of soft dorsal, those of the thoracic region small. 

 Dorsal XIII (XII-XIV) 11-12, the spines subequal or only 

 slightly increasing from the fourth or fifth, the last § the 

 length of hcnd. Anal III 7-8. Soft dorsal and anal not 

 scaly at the base, considerably produced. Pectoral longer 

 than the head, extending to above the anal spines. Caudal 

 truncate. Caudal peduncle about as long as deep. Oliva- 

 ceous ; a dark spot on the upper part of the base of caudal ; 

 soft dorsal sometimes spotted. 



II. Amazon. 



IIetdrogr.^mma, gen. nov. 



Mesopx (part.), Giintb. Cat. Fish. iv. p. 311 (1802). 



Gcophaf/us (part.), Cope, Proe. Ac. Philad. 1872, p. 2o0 ; Steind. Sitzb. 



Ak. Wien, lx.\i. l87o, p. 107 ; Eigenm. & Bra}', Ann. Ac. N. York, 



vii. 1894, p. 021. 

 Biotodoma* (non Eigenm. & Kennedy), Pellegr. Mem. Soc. Zoul. 



France, xvi. 1903, p. 180 (1904). 



♦ Eigenmann and Ikay proposed Mcsops cupidn as tlie type of Mesops. 

 Subsequent!}' the name Biotodu>nu wa.s given by Eigenmann and Kennedy 



