124 MR. G. A. BOULENGER ON THE [Feb. 18, 



It measures 118 millim., the external gill being 25 miUim. 

 long. In its development it is intei-mediate between the two 

 stages noticed above in P. lapraclii. The doi'sal spines are not 

 yet defined, the number of rays being 22 to the extremity of 

 the vertebral column ; the scales are imbi'icate, cycloid, with a 

 tendency to the rhomboid shape, rugose, with a smooth central 

 area corresponding to the pai-t of the scale first to appear. Six 

 blackish bars across the back, bifurcating on the sides ; below 

 these bars, two interrupted blackish lines run along each side. 



PoLYPTERUS ENDLiCHERi Heck. (Plate XI. fig. 2.) 

 I have seen only one young specimen of this PolyptertiSy 

 obtained at Abo, Nigeria, by Dr. Ansorge in October. It 

 measures 180 millim., the external gill 30, and corresponds in its 

 development with the largest specimen of P. lai^adii obtained by 

 Dr. Ansorge in the same locality. The spines number 11, and 

 are followed by 8 soft rays. The coloration does not differ from 

 that of the adult. 



PoLYPTERUS WEEKSi Blgr. (Plate X. fig. 3.) 



The type on which this species was established in 1898 

 is a young specimen, 170 millim. long, with external gills 

 measuring 15 millim., obtained at Monsembe, Upper Congo, 

 by the Rev. J. H. Weeks, from whom the British Museum has 

 since received a specimen 380 millim. long and without external 

 gills, obtained at the same locality. The young specimen, which 

 is here figured, is in what I have defined above as the third 

 pei-iod. It is dark olive above, yellow beneath, the two colours 

 sharply delimited on the side ; six narrow black bars across the 

 back, with some black spots between them, the last followed by 

 ii-regular marblings ; a large black spot on the membrane to each 

 dorsal spine ; soft fins with dark and light spots ; pectoral with 

 three blackish cross-bands. I have, already observed that the 

 asperities on the scales, which are so striking in the young, 

 disappear in the adult. 



PoLYPTERUS SENEGALUS CuV. (Plate XI. fig. 3.) 



This species differs from all its congenei'S in being of a uniform 

 greyish olive, without any markings, at least in specimens above 

 120 millim. total length; but the very young, with which we 

 have only quite recently become acquainted, are striped, as 

 described hereafter. The external gills appear to be lost very 

 early ; for they have not yet been found in any specimen above 

 90 milHm., although a large number of young have been examined 

 by Steindachner, Budgett, and myself. 



Two small specimens, measuring 60 and 69 millim. respectively, 

 were obtained by Mr. Loat in the White Nile, at the mouth of 

 Lake No, in the beginning of February 1901. In both, the 

 external gills aie present and measure 5 millim. The smaller 

 specimen has 8 spines and 8 soft rays to the dorsal, the larger 



