1902.] TOUXG OF POLYPTERUS. 125 



9 spines and 7 soft rays ; in both the 5 anterior spines are not 

 fully formed, not bicuspid, whilst the others have already assumed 

 their definite shape ; the caudal fin is long, with the median rays 

 pi'oduced, a little longer than the head ; the scales are imbricate 

 and rhomboidal, striated, except on the centi-al areola. A dark 

 brown band on each side, from the end of the snout, through the 

 eye and over the external gill, to the base of the caudal ; another 

 dark band, only a little narrower, below the first along the body, 

 separated fi'om it by a narrow yellowish streak. The very young 

 of P. senegcdus is therefore banded like that of F. lapradii, with 

 this difference, that the lower band is broader in proportion to 

 the upper. 



Dr. Ansorge's Nigeria collection contains several young with 

 external gills, obtained at Abo in October 1901 ; the leng-th of 

 these specimens varies between 39 and 105 miUim. In the 

 largest the external gill is present only on the left side and 

 measures 9 millim. ; the dorsal spines, 9 in number, are bicuspid, 

 the scales are nearly smooth, and mere traces of the dark bands 

 are visible : the other specimens agree entirely in their markings 

 with those obtained by Mr. Loat in the White Nile, and show 

 the complete passage from cycloidal to rhomboidal scales, and of 

 simple dorsal rays to pinnules with spines, the posterior of the 

 latter being developed first. 



PoLYPTERus PALMAS Ayres. (Plate XI. fig. 4.) 



This species is closely allied to P. senegalus, and in it also the 

 external gills do not persist long. I have only observed them in 

 one specimen 95 millim. long, where they measure 8 or 9 millim. ; 

 in all other specimens examined, measuring 80 millim. and above, 

 I have found them to be absent. 



The body is brownish above, yellowish beneath ; the upper 

 parts are marked with darker cross-bars, close together, which 

 branch off into marblings or i\. wide-meshed network on the sides, 

 enclosing roundish yellowish spots ; or the dark and light spots may 

 be arranged in chess-board pattern on the sides ; a blackish oval 

 spot on the peduncle of the pectoral fin. 



EXPLANATION OF THE PLATES. 

 Plate X. 



Fig. 1. Polijpterus lapradii Stdr., p. 123, young from Abo, S. Nigeria, slightly 

 reduced. 



2. Younger specimen of the same species, from Assay, S. Nigeria, nat. size, with 



(2 a) enlarged view of scales from the middle of the side. 



3. Poli/ptei'us weeJcsi Blgr., p. 124, young from Monsembe, Congo, nat. size, 



with (3 a) enlarged view of scales fi'om the middle of the side. 



Plate XL 



Fig. 1. Fohjpterus eongieus Blgr., p. 123, young, from Baugyville, Ubangi. 



2. Folypterus endliclieri Heck., p. 124, young, from Abo, S. Nigeria. 



3. Folypterus senegalus Cuv., p. 124, young, fi-om Assay, S. Nigeria. 



4. Folypterus palmas Ayres, p. 12.5, young, from Monsembe, Congo. 



[All figures of the natural size.] 



