264 PROCEEDINGS OF THE ACADEMY OF [Apr., 



line, thus allowing for the error of its inclusion in Astyanax, though 

 as a synonym of P. bimaculatus it must be suppressed. 



Serrasalmus rhombeus (Linnaeus). 



One 112 mm. long from Barro Alto. The back, above the lateral 

 line is marked with rather numerous, and in most cases more or 

 less dark brownish or dusky vertical spots. 



Pygocentrus piraya (Cuvier). 



Two examples, 160 and 214 mm. In the smaller specimen the 

 spots are larger, more distinct, and more sparse, also pale, and on 

 basal region of tail larger. 



Pimelodella graoile (Valenciennes). 



One 172 mm. long. Maxillary barbel reaches anal origin. Outer 

 mental barbel extends only for first fifth in depressed pectoral spine. 

 Adipose fin 2| in combined head and trunk length. 



Plecostomus jaguribensis sp: nov. Fig. 3. 



Head, measured to hind edge of occipital process, 3; depth 4f ; 

 D. I, 7; A. I, 4; P. I, 5; V. I, 5; lateral scutes from pectoral axilla 

 25 to caudal base and 2 more on latter; 5 scutes between dorsal 

 base and that of anal; 3 predorsal scutes; head width equals its 

 length, when measured from occipital process medianly behind; 

 head depth at occiput If; snout If; eye 6^; mouth width 3f, 

 mandibular ramus Q\; interorbital 2^; adipose fin 2|; pectoral 

 spine nearly 1; least depth of caudal peduncle 3j; ventral spine 1^. 



Body elongate, moderately depressed with convex surface above 

 and lower surface flattened, anterior profile well convex, and greatest 

 depth at dorsal origin. Caudal peduncle well compressed, and 

 length little less than least depth. 



Head large, moderately depressed, lower surface flattened, with 

 sides sloping up for about | greatest width of head, leaving wide and 

 broadly triangular occipital region, as seen in vertical section. Snout 

 wide, outline broadly triangular as seen from above, and its length 

 f its greatest width opposite front edges of eyes. Eye rounded, 

 well elevated or close to upper profile and center falls about f in 

 head length as measured to occipital process. Pupil small, appar- 

 ently vertical ellipsoid. Mouth moderately wide, anterior below. 

 Buccal disk orbicular, its transverse diameter li in snout length, 

 edges entire, and surface of lower portion outside with numerous 

 ■papilliB, of which innermost larger or better developed. Inside 

 jaws apparently more or less smooth. Inside upper jaw large 

 fleshy median papilla. Teeth slender, uniserial, long, bent over 



