238 Annals of the Carnegie Museum. 



Distribution. — Amazon; Matto Grosso; Paraguay. 

 The type of this species is about 150 mm. long. 



II. Genus Gastropristis gen. nov. 



Type, Serrasalmo {Pygocentrus) ternetzi Steindachner. 



This genus is very similar to Pygocentrus from which it differs in 

 the length of the anal. It is possible that the single specimen known, 

 150 mm. long, has met with some accident. If not, the species is 

 certainly the type of a new genus. 



Characters of Pygocentrus, but the origin of the anal on the vertical 

 from a point midway between the dorsal and adipose fins. Adipose 

 fin not rayed in the adult. 



Range that of the single species. 



3. Gastropristis ternetzi (Steindachner). 



Serrasalmo {Pygocentrus) ternetzi Steindachner, Anz. K. Acad. Wiss. Wien., 



1908, p. 359 (Descalvados on the Paraguay). 



Known only from the following description of Steindachner. 



"Head 2.6; depth i 4/7; D. II, 15; A. Ill, 12; scales 38 to 40-86 

 + 7-40 to 43; serrae in front of anus 27; e}-e 5 in the length of the 

 head; interorbital 2.25; snout 2.33; base of anal 2.25; height of anal 

 2.33: base of dorsal 1.6; height of dorsal 2.25; length of pectoral 1.6; 

 \'entral 3; depth of caudal peduncle 2.75. 



" Snout short, blunt; lower jaw heavy as in piraya; second suborbital 

 leaving a narrow naked margin behind; origin of dorsal midway 

 between snout and caudal, behind the vertical from the front of the 

 ventrals; adipose fin about 6 in the length of the head; pectoral not 

 reaching ventral; anal scaled at its base, its margin convex; last anal 

 ray about half as high as the first divided ray. Upper half of body 

 with obscure dark, round spots." {TransJaiioii.) 



III. Genus Pygocentrus Miiller & Troschel. 

 Pygocentrus Muller & Troschel, Horse Ichthyol., \'ol. I, 1845, p. 20. 



Type, Serrasalmo piraya Cuvier. 



Compressed, ventral surface with serrae from below the pectoral 

 to the anal; teeth compressed asymmetric incisors, more or less 

 notched, in a single series in each jaw. Palate without teeth; inter- 

 orbital very broad, the snout short, sometimes appearing abnormally 

 so, lower jaw short and very heavy; cheeks more or less completely 

 armed by the suborbitals; adipose fin rayed in the adult (over 125 

 mm.) ; anal long, with over twenty-five rays, its origin below the dorsal. 



