SOUTH AMERICAN NEMATOGNATHI. 205 



Only the types of this species are known. 



Body robust. Head not greatly 

 depressed; the profile steep; 

 greatest width of head If in 

 its length; greatest depth of 

 head 14-2: 



Eye 9-9J in head, 4 in snout, 

 2f-3J in interorbital, 22 J diameters behind the angle 

 of the mouth. 



Gill-rakers 5+12-14. 



Dorsal spine 3 in head, the rays 2 in head. Base of 

 adipose fin \ longer than base of anal. Pectoral spine 

 as long as the dorsal spine. 



Veritrals not extending more than \ their length be- 

 yond the vent. Membranes of all the fins thick. 



Ventral surface plain; upper parts brownish with 

 numerous darker spots, which are smallest on head and 

 on lower parts of the sides. All fins similarly spotted. 

 Rarely uniform reddish brown. 



Head 3J; depth 5-6; Br. 8-9; D. I, 7; A. 12-13. 



XXXIV. HEMISORUBIM. 



Platystoma Cuv. & Val., Hist Nat. Poiss. xv, 27, 1840, 

 (sp.) (preoccupied in Diptera). 



Hemisorubim Bleeker, Nederl. Tijdschr. Dierkunde, 

 1863, 97 (platyrhynchos). 



Type: Platystoma platyrhynckos Cuv. & Val. 



This genus differs from all the others in having the 

 upper jaw thin and truncate; shorter than the lower jaw; 

 snout narrowed, the width at the angle of the mouth 1J 

 times in the greatest width of the head; mental barbels 

 approximated and placed near the edge of the lip; inter- 

 maxillary band of teeth much shallower at the middle 

 than at the ends; the palatine patches are large. The 

 occipital process shorter than the dorsal plate and meet- 



