SOUTH AMERICAN NEMATOGNATHI. 37 



On account of the great variability of the palatine 

 teeth and pectoral spine in the specimens examined we 

 have placed longispinis in the synonymy of marinus. 



Rather robust, with slender caudal peduncle; the 

 greatest width less than the depth. Head short, its 

 greatest width H-1J in its length, the depth at the 

 occipital process about equal to the greatest width; pro- 

 file not very steep. Occipital process broader at base 

 articulating with the dorsal plate; occipital process 

 granular, covered with thin skin, the post orbital por- 

 tion of head sometimes granular; the fontariel not con- 

 tinued behind the eye except as a groove to the base of 

 the occipital process; the head nowhere as porous as in 

 gronovii. 



Eye 1-1J in snout, 2-2J in interorbital, 4-5 in head. 



Maxillary barbels extending to the vent in young, not 

 to base of ventrals in adult specimens. 



Upper jaw slightly longer; intermaxillary band of 

 teeth as in gronovii', vomerine and palatine patches very 

 variable, sometimes united, forming a single band, 

 sometimes the patches of the vomer are united but 

 separate from the palatine patches; 

 again the vomerine patches are 

 separate but joined to the palatine 

 patches, and in some cases all the /) 

 patches are separate giving four (/ 

 distinct patches on the roof of the mouth. 



Gill-membranes united and narrowly joined to the 

 isthmus. Gill-rakers 3+6. 



Distance of dorsal fin from tip of snout 3 in the 

 length, slightly less in the adult; the spine granular 

 toothed in front, 1J-1-J in head, the filament reaching 

 scarcely to the adipose fin in the adult. Distance of the 

 adipose behind the dorsal fin 3 in the length, in adult, 

 2| in young specimens. 



