Mr. G. A. Boulenger on a new Species o/Mormyras. 193 



We may sum up our results as follows : — In the Schizo- 

 pods and in the abranchiate larvse of Decapod Crustacea 

 respiration is purely cutaneous and is principally effected in 

 the membrane which clotlies the lateral walls of the carapace. 

 In the adult Decapods this respiratory apparatus persists, and 

 presents an absolute fixity, at any rate as far as regards its 

 large efferent canal ; but a secondary respiratory system is 

 added to that of the larva, and it is this latter system, in 

 which the branchise are intercalated, which is really the only 

 one described in the classic works. This branchial system is 

 undoubtedly the more important from a physiological point 

 of view (except perhaps in the terrestrial species) ; but it is 

 a secondary apparatus which in no way lessens the import- 

 ance of the cutaneous system. 



XXV. — Description of a neio Species o/'Mormyrus. 

 By G. A. Boulenger. 



Mormyrus mento. 

 D. 29. A. 36. V. 6. L. lat. 85. L. tr. H. 



Snout short, curved, once and a half the diameter of the 

 eye, fV the length of the head. Mouth terminal, on a line 

 with the lower border of the eye, its width one fifth 

 the length of the head. Teeth moderately large, notched, 

 five in the upper jaw, six in the lower. Diameter of the 

 eye one fifth its length, about two thirds the width of the inter- 

 orbital space. Chin strongly swollen. Origin of the dorsal 

 halfway between the gill-opening and the caudal, and above 

 the ninth ray of the anal. Pectoral as long as its distance 

 from the nostrils, extending a little beyond the base of the 

 ventral, which measures nearly half the length of the head. 

 Depth of body 3^ times in total length (without caudal), 

 length of caudal peduncle 5^ times ; depth of caudal peduncle 

 one fourth its length. 12 scales round the caudal peduncle. 

 Silvery, with fine brown dots, which are very crowded on the 

 head and the dorsal and ventral lines. 



Total length 190 millim. 



Closely allied to M. senegalensisj Stdr,, from which it is 

 distinguished by the smaller scales and the more slender 

 caudal peduncle, and to M. cyprinoides^ L., which has smaller 

 teeth and a deeper caudal peduncle surrounded by 16 scales. 



A single specimen, from the Gaboon. 



