SOUTH AMERICAN NEMATOGNATHI. 407 



occipital process, the occipital bordered usually by a 

 single plate behind. 



Tip of snout usually granular, sometimes with a tri- 

 angular naked area. 



Eye 3J-4J in the snout, 6^-8 in the head, 3-3J in the 

 interorbital. 



Belly entirely covered with minute scales. 



Base of dorsal fin equal to its distance from the adi- 

 pose fin, or from the caudal; first rays of the dorsal 

 much higher than the posterior, equal to the length of 

 the head; or not much higher than the last rays. 



Outer caudal rays produced; shortest caudal rays 1J 

 in the head or shorter. 



Color very light brown to nearly black, everywhere 

 spotted with darker; the spots smallest on the head; 

 spots on the belly sometimes scarcely larger than those 

 on the head, sometimes 4-6 times as large. 



Head 3-3-J. Lat. 1. 26. 



Twenty-seven specimens. Silva, Lake Saraca; Para; 

 Hyavary; Coary; Rio Puty; Surinam. 



350, Plecostomus vaillanti, 



Plecostomus vaillanti Steindachner, Siisswasserfische siidostl. Bras. 



iv, 9, 1877 (Rio Preto): Eigenm. & Eigenm. Proc. Cal. Acad. 



2d Ser. i, 169, 1888 (Eio Puty; Eio Preto; San Gongallo.) 

 Habitat: East Central Brazil. 



Head rounded in front, superciliary edge greatly raised, 

 a prominent ridge from the nares to the eye, a less 

 prominent one from the eye to the occiput; occipital 

 strongly keeled, terminating in a broad, short, process; 

 margined by three nuchal plates. Upper lateral plates 

 scarcely keeled; humeral keel indistinctly evident on the 

 caudal portion of the body. Tip of the snout granular. 



Eye 4-4| in the snout, 7-8J in the head, 2|-3 in the 

 interorbital. 



Belly entirely covered with scales, except around the 

 ventrals. 



