20 ]\Ir. C. T. Regan 07i the 



deep stron<^ly coni])ressed body, with the thorax and abdomen 

 expanded into a sharp-edged semicircular disc ; the pelvic 

 fins are very small and tlie pectorals are long, 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 ; 

 1 the radials are represented by a sirigle short and broad bone, 

 ' with a concavity fitting the broad convex articulating surface 

 of the hypercoracoid. 



In most other characters Gostropelecus is not unlike 

 Tetrogonopterus, except that there is no fontanel and ratlier 

 prominent longitudinal ridges border the well-developed 

 niuciferous channels on the upper surface of the head. 



Family 3.^ Xiphostomatidae. 



Osteological characters of the Characidse, but the small 

 maxillary is firmly united by suture with the very long pra3- 

 niaxillary and the upper jaw is somewhat movable. The 

 snout is produced and t'lC mouth is largp, with the teeth in 

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

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

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

 dorsal and anal fins are sliort, posterior. 



South American ; carnivorous, pike-like fishes. 



Xiphottoina, Luciocharax. 



Family 4. Anostomidae. 



Upper jaw movable, the prsemaxillaries articulating with a 

 pair of antero-lateral sessile facets on the mesethraoid ; 

 maxillaries movably articulated with or adherent to the prse- 

 maxillaries. Teeth, when well developed, compressed in- 

 cisors ; palate toothless. Pterygoid rather broad posteriorly, 

 overlapping the quadrate. Orbitosphenoid connecting ali- 

 sphenoids and parasphenoid, nearly or entirely separated 

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

 or ciliated ; lateral line straight. 



These fishes are South American. 



The genera may be arranged thus : — 



1. Mouth small, non-protractile; lips thick. Prsemaxillaries trian- 

 gular : inner ends of maxillaries articulating' with mesethmuid ; 

 rami of lower jaAV short and stout. Quadrate firmly united to 

 pterygoid and prseoperculum (PL U. fig. 1) ; hyomandibular as 

 iu the Characidse. i^Anostomince.) 



