20 ^h-. C. T. Regan on (he 



deep strongly conipres.-^etl body, with the thorax and abdomen 

 expanded into a sharp-edged semicircular disc; the pelvic 

 fins are very small and the pectorals are lonjr, with the rays 

 very strongly branched, except the first, which is stout and 

 simple. The pectoral arch is quite unique in structure; the 

 hypocoracoids are ankylosed, forming a single bone, which is 

 expanded below into a very large lamina that somewhat 

 resembles a half-folded fan, the prominent radiating ridges 

 of one side corresponding to the hollow grooves of the other ; 

 the radials are represented by a single short and broad bone, 

 with a concavity fitting the broad convex articulating surface 

 of the hypercoracoid. 



In most other characters Gastropelecus is not unlike 

 Tetrngonopterns, except that there is no fontanel and rather 

 prominent longitudinal ridges border the well-developed 

 niuciferous channels on the upper surface of the head. 



Family 3. Xiphostomatidffi, 



Osteological cliaracters of the Characidse, but the small 

 maxillary is firmly united by suture with the very long pra^- 

 raaxillary and the upper jaw is somewhat movable. The 

 snout is produced and tlie mouth is largv, with tlie teeth in 

 the jaws small, uniserial ; a band ofc" minute teeth is present 

 on the pterygoid; the scales are ciliated, the lateral line, 

 when present, runs along tiie middle of the side, and the 

 dorsal and anal fins are sliort, posterior. 



South American ; carnivorous, pike-like fishes. 



Xiphoi^toma, Lucwcharax. 



Family 4. Anostomidae. 



Upper jaw movable, the prffimaxillaries articulating witli a 

 pair of antero-lateral sessile facets on the mesethmoid ; 

 maxillaries movably articulated with or adherent to the prie- 

 maxillaries. Teeth, when well developed, compressed in- 

 cisors ; palate toothless. Pterygoid rather broad posteriorly, 

 overlaj)ping the quadrate. Orbitosphenoid connecting ali- 

 sphenoids and parasphenoid, nearly or entirely sejmrated 

 from the frontals. Dorsal fin median, short ; scales cycloil 

 or ciliated; lateral line straight. 



These fishes are South American. 



The genera nniy be arranged thus : — 



1. Mouth siimll, noii-protraclile ; lips thick. rnvmaxillavies trinn- 

 giiiiir : iinKT nuda of uiaxiUurit's articuhiting with incsethiucid ; 

 rami ot lower jaw short and ^toiit. Quadiato liriuly united to 

 pterygoid and prieoperculuni (I'l. II. ti^. 1) ; hyomaudibuhu- as 

 in tlie L'haracidie. {Anostomiuce.) 



