42. ICHTHYBORUS. 363 



compressed triangular teeth laterally ; its inner surface, which forms 

 the anterior part of the roof of the mouth, is covered with minute 

 pointed teeth. The dentaries of the mandible also are coalescent 

 into a single bone, without median suture ; their dentition is the 

 same as that of the upper jaw, but there are three canine teeth, the 

 central tooth standing in front of the jaw and fitting between the 

 upper canines. The maxillary is very small, attached to the extre- 

 mity of the intermaxillary. Palate toothless. Nostrils in front of 

 the eye, close together, the posterior wide, open. Gill-openings wide, 

 the gill-membranes being separate ; gill-rakers short, lanceolate. 

 Nile. 



For our first acquaintance with the fishes of this genus we are 

 indebted to Joannis, who gives a description and figure which do not 

 leave any doubt as to the generic affinity of the fishes found by him, 

 and rediscoverd by Mr. Petherick on his last expedition to the Upper 

 Nile. I have long hesitated to separate them specifically, but as 

 Joannis says that there are only fifteen scales in a transverse row, 

 and as he represents in the figure the scales of»a corresponding size, 

 it appears probable that the Nile is inhabited by two distinct species. 

 They must be very scarce, as Joannis and Petherick are the only 

 traveLers who had the good fortune of meeting with them. It is 

 also worthy of notice that only two examples were in the extensive 

 collections made by Mr. Petherick, which appears to confirm the 

 remark made by Joannis that these fishes are always found in pairs. 



1. lchthyborus microlepis. 



B. 4. D. 15-17. A. 15-16. P. 14-15. V. 10. L. lat. 100. 

 L. transv. 12/14. 



The height of the body is contained four times and three-fourths 

 or five times and one-fourth in the total length (without caudal), the 

 length of the head thrice and one-fourth or thrice and two-thirds ; 

 the diameter of the eye is somewhat less than the width of the 

 interorbital space, one-half of the length of the snout, and two-fifths 

 of that of the postorbital portion of the head. Intermaxillary with 

 nineteen, mandible with fourteen teeth on each side. Cheek quite 

 naked, the suborbital ring being narrow. Operculum with radiating 

 striae, twice as high as long. The origin of the dorsal fin is nearer 

 to the root of the caudal than to the extremity of the snout; it is 

 higher than long. Anal fin somewhat longer than high; caudal 

 with the lobes rounded, two-thirds as long as the head. Pectoral as 

 long as the ventral, rather more than half as long as the head ; the 

 pectoral does not extend to the ventral, which terminates at a great 

 distance from the vent. Uniform silvery ; dorsal rays with some 

 faint dots ; caudal with five or six rather irregular transverse series 

 of round black spots. 



Upper Nile. 



a-b. Six and a half inches long. Chartoum. From Consul Pethe- 

 rick's Collection. 



