APPENDIX C. 
2(57 
merit and that of the anal fin being less than the length of the 
head. 
GYMNODONTIDJ^. 
Tetrodon. 
Jaws trenchant, without teeth, with a median longitudinal 
groove; body extensible, covered with a rough spiny skin. The 
oesophagus can be filled with air, so that these fishes can float on 
the surface of the water, belly upwards. 
Tetrodon lineatus, Forsk. (Fah-haka.) 
Back and sides with brownish-black longitudinal bands ; abdomen 
without bands. 
GANOIDEI. 
POLYPTERUS. 
Body elongate, covered with hard, smooth, rhombic scales. Jaws 
with a series of conical teeth, behind which are bands of smalle 
teeth. Along the back a series of separate spines, each of which 
bears an articulated finlet. 
Polypterus bichir, GeolF. 
With about sixteen dorsal finlets. 
