SOUTH AMERICAN NEMATOGNATHI. 413 



Belly mostly naked; sometimes a few minute rough 

 scutes below the pectoral; a triangular patch of similar 

 scutes between the gill-opening and the rictus, which is 

 sometimes reduced to one or two scutes. 



Base of the dorsal fin longer than its distance from the 

 adipose fin. 



Caudal fin slightly emarginate, the shortest ray being 

 1| in the head. 



Upper surface of the pectoral spine covered with re- 

 curved bristles which are strongest and longest near the 

 tip of the spine. 



Dorsal surface and sides thickly covered with dark 

 roundish spots, the spots on the head smallest; ventral 

 surface plain. A single series of spots between two dor- 

 sal rays. 



Lat. 1. 26. Head 34-3|. 



Two specimens .21 m. Rio Una. 



367. Plecostomus wuchereri. 



Plecostomus luuchereri Gtinther, v, 335, 1864 (Bahia). 

 Habitat: Kio Mucuri to Bahia. 



This species is very closely related to PL robinii C. & V.; 

 it differs in the markings of the fins, and the transverse 

 profile of the head is less regularly convex; the ventral 

 surface more granular. Head 3i. 



Two specimens, .27-. 25 m. Rio Pedra. 



368. Plecostomus johnii. 



Plecostomus johnii Steindacliner, SB, Ak. Wieu, Ixxiv, 1876, Siiss- 

 wasserfisclie siidostlichen Brasilieus, iii, 133 (Rio Puty; Rio 

 Preto); Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 170, 171, 

 1888 (Rio Preto; Rio Puty). 



Habitat: Rio Preto; Rio Puty. 



Head broad, rounded in front, snout not keeled, reg- 

 ularly convex in transverse profile; superciliary edge 

 raised. 



Eye 4 in the snout, 6| in the head, 24 in the interor- 

 bital. 



