38. XIPHORHAMPHUS. 353 



37. OLIGOSARCUS. 



Dorsal fin placed in the middle of the length of the body, above 

 the space between ventrals and anal ; anal long. Head and body 

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

 line complete; belly rounded. Cleft of the mouth wide; teeth 

 conical, in a single series in the intermaxillary, maxillary, mandible, 

 and on the palatine bones ; some of the teeth in the intermaxillary 

 and mandible are canine teeth. Nostrils close together. Gill- 

 openings very wide, the gill-membranes not attached to the isthmus ; 

 gill-rakers slender, lanceolate. 



Brazil. 



1. Oligosarcus argenteus. 

 D. 11. A. 25. V. 8. L. lat. 43. L. transv. 9/7. 



The height of the body is nearly equal to the length of the head, 

 which* is two-sevenths of the total (the caudal fin not included) ; the 

 depth of the head equals its length without snout ; -the width of the 

 interorbital space is a little less than the diameter of the eye, which 

 is one-fourth of the length of the head, and equal to the extent of 

 the snout. Cleft of the mouth wide, the maxillary extending some- 

 what behind the vertical from the centre of the eye ; the intermax- 

 illary has two or three feeble canine teeth on each side, the anterior 

 pair being received between the front canine teeth of the lower jaw, 

 which are twice as strong as the upper ones. The lateral teeth of 

 the mandible and those of the maxillary and of the palatines are 

 equally small. Nearly the entire cheek is covered by the infraorbital 

 bones, only a narrow space above the prseopercular limb remaining 

 naked. The operculum is slightly emarginate behind, and twice as 

 high as long. The origin of the dorsal fin is exactly in the middle 

 between the end of the snout and the root of the caudal fin, and a 

 little behind the insertion of the ventrals ; its last rays are opposite 

 to those of the anal. Caudal deeply forked, shorter than the head ; 

 the pectoral extends to, or somewhat beyond, the root of the ventral 

 fins ; the ventral is shorter than the pectoral, rather more than half 

 as long as the head, and extending to the vent. 



The two specimens, which have been preserved in spirit for a long 

 time, are light brownish, shining silvery. A silvery band runs along 

 the middle of the body, and terminates in an oblong black spot be- 

 fore the root of the caudal. 



Brazil. 



a-b. Three and a half inches long. 



38. XIPHORHAMPHUS. 



Xiphorhamphus, sp., Mull. 8f Trosch. Hor. Ichth. i. p. 32. 

 Xiphorhynchus; sp., Cuv. fy Val. xxii. p. 336. 



Dorsal fin placed behind the middle of the length of the body, 

 between ventrals and anal ; anal long. Head and body more or less 

 elongate, covered with small scales ; lateral line complete. Belly 



vol. v. 2 a 



