74 SILURIDJS. 



cated in front, its greatest width being four-fifths of its length ; upper 

 jaw overlapping the lower. Nasal barbels slender, not so long as 

 the snout ; the maxillary barbels extend to the end of the pectoral, 

 the outer ones of the mandible to the root of the pectoral. The teeth 

 on the palate form four narrow bands of nearly equal length, the 

 vomerine band being interrupted in the middle and not continuous 

 with the palatine band. The upper surface of the head coarsely gra- 

 nulated, the granules being arranged in striae. Occipital process not 

 much larger than, and similar in shape to, the triangular basal bone 

 of the dorsal spine. Dorsal spine strong, slightly serrated along both 

 edges, more than half as long as the head. Adipose fin short, sub- 

 divided into rays only along its upper margin in young individuals ; 

 in old specimens the division into rays extends to the base of the fin, 

 and the first ray is changed into a hard, pungent spine. Caudal 

 forked ; both lobes equal in length, or the lower rather longer. Pec- 

 toral spine as long as, but stronger than, that of the dorsal fin, serrated 

 along both edges, slightly exteriorly and strongly interiorly. Ventral 

 rather shorter than pectoral. Dark grey above, white below; a' 

 blackish blotch behind the gill-opening ; a broad blackish band along 

 each caudal lobe. 



The transformation of an adipose fin into one with rays and spines 

 in this fish is a very curious fact. I have no doubt that very young 

 specimens arc provided with a fin without any indication of rays. 

 Riippell, when he described the species from a young specimen (4^ 

 inches long), did not observe anything peculiar in its fins. Clarotes 

 la uglinii (Kner, 1. c. taf. 1 &2, and Hyrtl, ibid. p. 371, and the latter 

 in Denkschr. Wien. Acad. L859, xvi. p. 1) is certainly nothing but a 

 deformed specimen of the same species ; the arrangement of the gra- 

 nulated plates on the upper surface of the head, as represented by 

 Hyrtl on pi. 2, is exactly the same as in our adult specimen. 



The species appeals to be peculiar to the Upper Nile, although 

 single specimens, like that described by RiippeU, may be carried 

 down towards the mouth of the river. 



a. Fine specimen, 16 inches long. Chartoum. From Consul Pethe- 

 riek's Collection. — The spine of the adipose fin is completely 

 formed. 



/>. Eight inches long. Chartoum. From Consul Petherick's Col- 

 lection. — One-half of the adipose fin is transformed into rays. 



cd. Six and seven inches long. Chartoum. From Consul Pethe- 

 rick's Collection. — The division into rays is only visible on the 

 margin of the adipose fin. 



31. MACRONES*. 



Macronea, Dumeril, Ichthyol. Anal. p. 484 



Hypselobagrus, Macrones, Hemibagrus, et Aspidobagrus, Bleek. Ne- 

 derl. Tydschr. Dierk. 1803, p. 96. 



Adipose fin long, or of moderate length ; a short dorsal with a 

 * 1. Pimclodus uicnoda, Ham. Bueh. p. 203. — Pimelodus comila, H. B. Fish. 



