170 Apodal Fishes of Bengal, 



tudinal opening to the branchiae, but in which the gills appear 

 to be fully developed. 



This genus coming after, as it could not (in consequence 

 of the longitudinal direction of the branchial aperture) come 

 before Pneumabranchus, evinces a return of the affinities 

 from the Amphibious character of that genus. This is still 

 more perceptible in the succeeding genus Ptyobranchus, in 

 which the restoration of the pectoral fins evinces a return of 

 the affinities from the Amphibious type to the ordinary cha- 

 racter of fishes, still better marked by two branchial aper- 

 tures, as well as two pectoral fins. 



Thus we observe in passing from one extremity of the 

 order to the other, a regular succession of affinities leading 

 from a short flat, to an elongated narrow head, and from 

 thence to a prominent development of fins on the anterior 

 parts of the body, with a corresponding deficiency behind ; 

 from thence we return again to the great development of fins 

 behind, with a corresponding deficiency on the anterior 

 parts, thus completing the circle of the first tribe. Recom- 

 mencing again where we left off, we pass through species 

 almost destitute of any fins whatever, and losing even the 

 gills of fishes which become partially replaced by organs 

 suited to amphibious respiration. Still led by the succes- 

 sion of affinities, we are conducted back to the character- 

 istic form of fishes, distinguished once more by fins and gills. 



The result is, that the affinities of Apodal fishes are 

 circular throughout the order, as well as in each of the 

 minor groups here proposed, and that they will be found to 

 afford numerous analogous, or corresponding points with the 

 various other orders of fishes. 



III. — On the Classification of Apodal Fishes, 



The following is the manner in which we dispose of the 

 classification of this order, founded on the characters of 

 Indian species. 



