SOUTH AMERICAN NEMATOGNATHI. 405 



346b, Plecostomus commersonii scabriceps. 



Plecostomus commersonii scabriceps Eigenm. & Eigenm. Proc. Cal. 

 Acad. 2d Ser. i, 168, 1888 (Sao Matheos). 



Three specimens .30-. 35 m. from Sao Matheos. 



Large spots, the occipital process shorter than in com- 

 mersonii; the pectoral spine in two specimens with curv- 

 ed bristles near the tip, the lower portion of the head 

 naked except a triangular area immediately in front of 

 the gill-openings. 



347. Plecostomus limosus. 



Plecostomus limosus Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 

 167 and 168, 1888 (Kio Grande do Sul). 



Allied to Plecostomus plecostomus Linnaeus. 



All the scutes with a distinct median keel, the humeral 

 keel being continued back. 



Occipital bone margined by a single large nuchal 

 plate; occipital keel more blunt than in plecostomus. 

 Tip of snout naked, the snout more rounded than in 

 plecostomus. Interorbital 2 in the head to the end of 

 the opercle. 



Eye 4J-5 in the snout, 8-9 in the head, 3-3 in the 

 interorbital. 



Outer caudal rays little produced, middle caudal rays 

 much longer than in plecostomus, 1|-1| in the head. 



Base of the dorsal fin equals its distance from the 

 caudal, or a very little less. 



Lat. 1. 28. 



Otherwise similar to PI. plecostomus Linn. 



Types No. 7869. Four specimens .25 m. Rio Grande 

 do Sul; from the Emperor's collection. 



348, Plecostomus carinatus, 



Plecostomus carinatus Steindachner, Flussfische Siidamerika's, ii, 

 108, plate iv, fig. 2, 1881 (Jatuarana; Ueranduba and Lake Sa- 

 raca). 



Habitat: Amazons. 



One specimen; Jutahy. 



