Apodal Fishes of Bengal. 167 



a branchial sack of which there is no other example in the 

 animal kingdom, and which seems to be a special provision 

 by means of which, nature passes from the purely aquatic 

 type, to animals adapted to the respiration of air. 



Affinities of Apodal Fishes. — The sequence of genera 

 resulting from the Analysis of Indian species as far as it 

 goes, corresponds nearly with that previously attained by 

 Baron Cuvier, as may be seen on comparing the order as 

 it stands p. 153, with our own results p. 158-59. 



The nine first genera of Cuvier's list, p. 153, form the only 

 portion of the order which we have been able to illustrate 

 with Indian species. Two of the genera we have been 

 unable to adopt, and to the remaining seven, we have ad- 

 ded ten additional genera, the whole being separated into 

 two tribes and five families, to which we have endeavoured 

 to assign natural characters. 



Without referring to the general affinities of Fishes,* it 

 will be sufficient on the present occasion to notice those of 

 Apodal species merely. 



Commencing with the genus Anguilla, Cuv. we perceive 

 a very great difference of form between the flat, triangular, 

 depressed head, tessellated scales, and broad projecting 

 lower jaw of Anguilla brevirostris, as compared with the 

 naked skin, and compressed narrow head of Anguilla 

 acutirostris which leads to the genus Conger, in which 

 the head is narrow, and the jaws and fins more elongated, 

 passing into the form of Muraenesox. From this last the 

 transition is easy and natural to the genus Leptognathus 

 ofSwainson, both these genera having elongated narrow 

 pointed jaws. In the first, the dorsal fin attains its maxi- 

 mum development, having advanced in front of the pec- 



* On this subject the reader is referred to the letter of Mr. W. S. Macleay, vol. 

 ii. p. 263. It would be difficult to express the extent of our obligations to that 

 great naturalist, for the rough outline in question. 



Z 



