SOUTH AMERICAN NEMATOGNATHI. 29 



der, the alimentary tract and opercle serve to separate 

 this family from the other Nematognathi. 



SUBFAMILY TACHISUKINJE. 



ANALYSIS OF THE AMERICAN GENERA AND SUBGENERA OF TACHISURINJE. 



a. Mental barbels none. Head greatly depressed, keeled behind. Occi- 

 pital process becoming narrower behind, meeting the dorsal spine. 



PARADIPLOMYSTES vi. 



aa. Mental barbels two. Maxillary barbel broad, band-like. Pectoral 

 spine and usually the dorsal spine with long band-like filaments. 



AlLTJRICHTHYS VII. 



aaa. Mental barbels four. Maxillary barbels usually short, not band-like. 

 Head not greatly depressed. 



b. Palatine teeth in numerous small patches which are aggregated on 

 two fleshy cushions, one on either side of the arched palate. Mandi- 

 bulary teeth disappearing with age. Intermaxillary band of teeth 

 with backward projecting angles of separate patches of teeth. 



GENIDENS vin. 



bb. Palatine teeth fixed; both jaws with teeth. TACHISTJRUS ix. 



A. Head and occipital process entirely covered with skin and muscle; 



occipital process sparingly granulated. (Galeicthys.) 



AA. Occipital process and bones of the head usually exposed, skin 



thin; crown of head and occipital process granular. 



c. Palatine patches of teeth with a backward projecting angle on 

 the inner margin. 



D. Dorsal plate enlarged. (Sciadeichthys.) 



DD. Dorsal plate crescent shaped, not enlarged. 



E. Occipital process narrowed or constricted at base. 



(Notarius.) 



EE. Occipital process widest at base. (Netuma.) 



cc. Palatine patches of teeth without a backward projecting angle 

 on the inner margin. 



F. Eye above the level of the mouth; gill rakers 25 or 

 fewer. 



G. Teeth on the palate villiform. (Hexanematichthys.) 



GG. Teeth on the palate granular; no teeth on vomer. 



Gill membrane not forming a free margin across the 



isthmus. (Tachisurus.) 



FF. Eye not above the level of the mouth; gill rakers long 



and slender, 40 or more. (Cathorops.) 



VI. PARADIPLOMYSTES. 



Paradiplomystes Bleeker, Nederl. Tijdschr. Dierkunde, 

 i, 1863, 92 (coruscans). 



