CHAEACINID^. -611 



teeth in loth jaws well developed and conical ; gill membranes 

 free from the isthmus; nasal openings close together. South 

 America and Tropical Africa. Fishes of prey. 



Hydrocyon. — The dorsal fin is in the middle of the length 

 of the body, above the ventrals ; anal of moderate length. Body 

 oblong, compressed, covered with scales of moderate size ; belly 

 rounded. Cleft of the mouth wide, without lips ; the inter- 

 maxillaries and mandibles are armed with strong pointed teeth, 

 widely set and few in number ; they are received in notches of 

 the opposite jaw, and visible externally when the mouth is 

 closed. Palate toothless. Cheeks covered with the enlarged 

 suborbital bones. Orbit with an anterior and posterior adipose 

 eyelid. Intestinal tract short. 



Four species from Tropical Africa ; two occur in the Nile, 

 Sf. forskalii being abundant, and well known by the names 

 "Kelb el bahr" and "Kelb el moyeh." Their formidable 

 dentition renders them most destructive to other iishes ; they 

 grow to a length of four feet. 



Cynodon. — Dorsal fin placed behind, or nearly in, the middle 

 of the length of the body, behind the ventrals ; anal long. 

 Head and body compressed, oblong, the latter covered with very 

 small scales ; belly compressed, keeled. Teeth in the inter- 

 maxillary, maxillary, and mandible in a single series, conical, 

 widely set, of unequal size ; a pair of very large canine teeth 

 anteriorly in the lower jaw, received in two grooves on the 

 palate ; palate with patches of minute granulated teeth. The 

 outer branchial arch without gill-rakers, but with very short 

 tubercles. 



Four species from Brazil and the Guyanas ; they are as 

 formidable fishes of prey as the preceding, and grow to the 

 same size. 



With the exception of Sarcodaces, all the remaining genera 

 of this group belong to the fauna of Tropical America, viz. 

 Anacyrtus, Rystricodon, Salminus, Oligosarcus, Xiphorhamphus, 

 and Xiphostoma. 



