194 Apodal Fishes of Bengal. 



posed of about 30 very fine sharp teeth, which at the apex form a cres- 

 cent with those of the opposite side. The palatine teeth form an inner 

 row. They are stronger, placed at intervals from each other, short, 

 hooked and sharp. Their number varies a little in different indivi- 

 duals, but they are generally twelve or thirteen on either side. The 

 lower jaw is furnished with a single row (about 20 in number) of 

 precisely similar, but smaller teeth than those of the palatines ; the 

 edge of the jaw becomes broader in front at the symphysis, where the 

 teeth become somewhat crowded. See Jig. 2a. b. 



The gills have three strong, short bony arches; but no branchial 

 combs, except a few thick fleshy points on the outside of the middle 

 arch. The intervals between the branchial arches are nearly obli- 

 terated by means of a membrane, in which there is only a narrow 

 aperture behind each arch, as well as the opening in front of the first 

 arch. See Jig. 4. 



Over the end of the first arch, there is a narrow aperture leading into 

 a moderate sized sack, which as well as the membrane between the 

 branchial arches is lined with a fine net-work, consisting of the 

 extreme branches of the branchial arteries and veins,, which form 

 numerous little vascular tufts dispersed over every part of the in- 

 ner surface of these organs. See Jig. 5. 



These perform the office of gills, for effecting the aeration of the 

 blood through the medium of water as well as air. 



The animal is thus enabled to live for a time in either medium, al- 

 though both are essential. 



A little behind the upper end of the third arch, there is a lunate group 

 of fine sharp pharangeal teeth, at the entrance to the oesophagus as 

 usual throughout apodal fishes, together with a row of similar teeth 

 extending from the posterior horn of the above group on one side, to 

 the corresponding portion of that of the opposite side, thus forming a 

 strong armature of sharp hooked teeth, guarding the entrance to the 

 throat. The great length of the oesophagus in ophicardious as com- 

 pared with other species, renders the function of pharangeal teeth very 

 important, in order to arrest the entrance of food until it is reduced to a 

 state in which it is likely to afford least danger to the animal by caus- 

 ing obstruction, which from the nature of the prey, would be liable 

 to happen 



The diaphragm separating the cavities of the thorax and abdomen, 

 is placed at a distance behind the branchial apertures greater than 

 these are from the extremity of the muzzle, or equal to about one-third 

 of the distance from the branchial apertures to the vent. The thorax is 



