194 CALIFORNIA ACADEMY OF SCIENCES. 



pressed. Head narrowed forward, its greatest width 1| 

 in its length; its width at the angle of the mouth about 

 2 in its length. Surface of the head covered with thin 

 skin. 



Eye 2-2i in the snout which is equal to the inter- 

 oribital. 



Maxillary barbel reaching beyond origin of dorsal; 

 mental and postmental beyond base of pectoral. 



Distance of origin of dorsal from tip of snout 2| in 

 the length. Dorsal without a basal plate or a spine. 



Distance of adipose from dorsal somewhat greater 

 than the length of the dorsal. Adipose fin low, joined 

 to the caudal. Caudal rays rapidly tapering to the mid- 

 dle ones, which are gratly prolonged, less than 2| in the 

 length. 



Anal rays all of about the same height. 



Ventrals long and narrow, inserted under the anterior 

 half of the dorsal and reaching half way to middle of 

 anal. Pectoral long lanceolate, without a spine. 



Uniform yellow. 



Head 4J ; D. 7; A. 13. 



XXX. Brachyplatystoma. 



Platy stoma Cuv. & Val. Hist. Nat. Poiss. xv, 1840, sp. 



Brcicltyplaty stoma Bleeker, Nederl. Tijdschr. Dier- 

 kunde, i, 1863, 97 (vaillanti). 



Piratinga Bleeker, 1. c. 99 {reticulata). 



Malacohagrus Bleeker, 1. c. 100 (Jilamentosus) . 



Type: Platystoma vaillanti Cuv. & Val. 



This genus differs from all other Pimelodincc in the 

 peculiarity of its dentition. The inner teeth of the in- 

 termaxillaries are long, slender and depressible; the 

 outer ones are shorter, stronger and recurved. The 

 teeth on the vomer and palatines are smaller than those 

 on the intermaxillaries. Caudal deeply forked. Branchi- 

 ostegals 11 or 12. Fontanel elongate elliptical. 



