68 



Proceedings of the Royal Physical Society. 



behind the teeth of the lower jaw, five small warty-like papillae 

 projecting behind it into the mouth. In front of the mouth 

 you have the free transverse slightly- fringed margin of the un- 

 divided nasal membrane, with its frenum in the mesian line, 

 attaching it to the upper jaw ; it is also free at its outer margins 

 (leaving an obliquely placed nasal opening on each side), and 

 thus forms altogether a double flap, which covers the large trans- 

 versely placed nasal organs. About 1 J inch behind the mouth, 

 the double row of spiracles or gill openings, five in number 

 on each side, run backwards in a curved direction ; and about 

 J an inch behind them, but in the mesial line, at the forepart 

 of the abdomen, you find a small projecting body which mea- 

 sures xoths of an inch in length by |th of an inch in breadth ; 

 it is 3 x 2 oths inches distant from the mouth, and from it to the 

 anal opening measures 4 inches ; it appears to be the last re- 

 mains of the now all but absorbed vitellus or yolk of the egg, 

 the umbilical bag which nourished the fish in its younger 

 stage of existence. The whole length of the fish along its 

 under surface is, from the snout to the middle of the anal 

 opening, 10 inches, and from the anal opening to the extre- 

 mity of its slender and pointed tail 30 inches. 



The tail is rounded above ; it measures about an inch in 

 breadth at its insertion to the body, and tapers to a minute 

 point. Nearly opposite the insertion of the spine above, there 

 begins on the under surface a narrow fin without rays, which 

 projects about one-tenth of an inch, and runs with a low and 

 free margin for about 3J inches down the grooved under-surface 

 of the tail. 



As this fish advances in age, its body and tail are described 

 as becoming very rough and spiny above, and, in some 

 instances, the tail is said to become comparatively short, at 

 least in the old male. The fish is described as using its tail 

 as a weapon of defence, striking its enemies with this for- 

 midable weapon, and inflicting severe and even dangerous 

 wounds. It is stated to feed on small eels, which are abun- 

 dant in the mud of the river's bed. 



It is with much diffidence I have ventured to lay before the 

 Society a notice of this African fish. It belongs to the Sub- 

 Family of the TrygonincB ; and if the peculiarity of the 

 spine or spur on the tail is a character of any importance, 



