1. LAKIMTTS. 267 



c. Half-grown. River Niger. From Mr. Fraser's Collection. 



d. Adult : skeleton, lliver Niger. From Mr. Fraser's Collection. 



Pseudobranchise well developed. Air-bladder simple. 



Sheleton. — The maxillary bone gradually widens from the base to 

 its extremity, which is not very broad. The intermaxillary is rather 

 slender, tapering to a very fine point, and is armed in aU its length 

 with a narrow band of fine villiform teeth, and with an outer series 

 of more distant and very small teeth ; its posterior processes extend 

 backwards to the level of the anterior margin of the eye, being one- 

 third only of the length of the bone ; there is, besides, a flat trian- 

 gular process nearly in the middle of its posterior margin. The mu- 

 ciferous channel of the mandibulary is not very deep, and divided 

 into four cavities by three feeble bony cross-bars. The tympanic 

 and pterygoid bones have a more solid osseous centre, and the rest 

 exceedingly thin and fragile. The anterior portion of the vomer is 

 triangular, excavated, with rather projecting anterior edges ; the 

 posterior is very feeble, tapering to a long, fine point. 



The bony ridges and crests at the upper surface of the skull are 

 peciiliarly arranged. The occipital crest is very elevated above the sur- 

 face of the skull, and its horizontal portion is rather higher than the 

 vertical ; it does not extend beyond the suprascapula. There is no 

 central cavity, but aU the cavities are arranged in pairs. The first 

 pair occupies the anterior portion of the frontal bones ; the second is 

 situated more in the centre of the distance between the eyes, and 

 occupies the middle of the frontals ; the third and fourth are elon- 

 gated, and placed more outwards, the latter immediately above the 

 upper posterior angle of the eye. There is a wide space between the 

 cavities of the third pair and the occipital crest, anoccupied by mu- 

 ciferous channels. The third and fourth pair are continued into the 

 channels of the infraorbital bones and of the suprascapula. The 

 praeorbital is narrow, about three times as long as broad, and has 

 four or five grooves. The turbinal bone is transformed into a half- 

 channel of moderate length. There are four grooves between the 

 ridges of the praeoperculum ; they are wide, not deep, and separated 

 from one another by narrow bony cross-bars. Only the angle of the 

 bone is distinctly serrated, the inferior limb exhibiting some obsolete 

 denticulations ; the posterior is entirely smooth. The operculum has 

 a deep angular notch, and no prominent spines, nor a ridge on its 

 interior surface ; the suboperculum is slightly notched before the 

 base of the pectoral fin ; the suprascapula is entire. 



The lower part of the skull is very much swollen, globular, with 

 a narrow groove along the medial line. 



The glossohyalis styliform, and rather broader anteriorly; the uro- 

 hyal is an elongate triangular plate, with a groove along its inferior 

 margin. The pubic bones have no posterior process, and are diver- 

 gent anteriorly. 



There are eleven abdominal and fifteen caudal vertehrce, the 

 length of the former portion of the column being to that of the 

 caudal as 1 : 1-26. The first intcrhaemal spine is rather strong, and 

 equals the length of the second vertebra to the sixth. 



