SOUTH AMERICAN NEMATOGNATHI. 207 



nearer base of ventrals than base of pectorals; with re- 

 trorse teeth behind. Adipose fin longer than anal. 



Lower caudal lobe wider and longer than upper, 

 rounded in adult; pointed in young. 



Ventrals extending | their length beyond the vent. 



Pectoral spine 1| in head, with equally strong teeth 

 in front and behind. 



White below; olivaceous above, with a few jet black 

 spots scattered on sides, usually a similar spot at base of 

 upper caudal lobe; fins plain. 



Head 3; depth 6-7; D. I, 6; A. 10; Br. 11. 



XXXV. PSEUDOPLATYSTOMA, 



Platystoma Agassiz, Gen. et Spec. Pise. Bras. 1829 (sp.) 



Sorubim Spix, Gen. et Spec. Pise. Bras. 1829 (sp.) 



Pseiidoplay stoma Bleeker, Nederl. Tijdschr. Dierkunde, 

 i, 97, 1863 (fasciatum). 



Hemiplaty stoma Bleeker, 1. c. (tigrinum.). 



Type: Silurus fasciatits Linna3us (in part). 



This genus consists of three closely related species and 

 several varieties. 



Upper jaw little longer than lower; teeth of the jaws 

 alike; vomerine and palatine patches of teeth more or 

 less united, the two forming a , -shaped patch on each 

 side of the palate; gill-rakers short, spine-like, not over- 

 lapping; caudal deeply lobed, the lobes rounded (except 

 in very young) the rays very much branched, giving 

 the fin a leathery texture. Branchiostegals 14 or 15; 

 barbels short. 



Adipose fin shorter than the anal; dorsal spine nearer 

 end of adipose fin than tip of snout. 



ANALYSIS OF THE SPECIES OF PSEUDOPLATYSTOMA. 



a. Body usually with vertical bars or lines interspersed with spots; some- 

 times plain dusky. 



