296 Dr. Hancock on the Composition of the Fin Rays 



Guiana, «^"fti^tic^ iriceriain ODS^rv^^^^ I had made 



on the silurii of Essequibo in 1825, and exhibited to those 

 excellent naturalists of the Zoological Society, Messrs. Vigors, 

 Bennett, and Yarrell, as well as an extraordinary and unique 

 species of articulation in the armature of the gilbagre, a near- 

 allied species of the same genus, at the museum of that society, 

 and to which, to save repetition, I bee leave to jefer .thejeader, 

 lor a further explanation. , - . , ,[ >, . r/f I-rfg 



We find the diversities in the structure of the air-bladder to 

 be very remarkable, even in closely-allied species. In the 

 herring, for instance, it is a detached cylindrical tube. In the 

 shad it is of the fixed kind, or a membrane stretched across, 

 as in the mackerel, mullet, &c. 



We find this organ most fully developed in the flying-fish of^ 

 the tropics {exocoetus volitans). One of these flew, in 1804, 

 on board of a vessel I was in, about the latitude of Barbadoes, 

 which afforded me the opportunity of dissecting a fresh 

 specimen. ,j,fi 



Since the^ above investigations were made, I have noticed ' 

 some very interesting remarks on the subject in the Anat. 

 Comp. of M. Cuvier, tome i., p. 501 ; and v., p. 270 — " De la 

 vessie natatoire des poissons ;^* and to which I beg leave to 

 refer the reader. I will only observe here, that what that 

 sagacious naturalist has there stated is sufficient to put authors 

 upon their guard how far they ought to repose confidence JOn: 

 various authorities and commonplace reports. rroihoca 



We may say, perhaps, with the utmost fairness, that ih 

 general, the more important, solid, and valuable improvements 

 in the arts and sciences either originate in Britain, or are there '1 

 developed in their greatest perfection. At the same time, the : 

 cultivators of certain of the physical sciences are, most incon- 

 trovertibly, far behind their continental brethren ; and it must * 

 be owing to the extremely loose and vague manner of em- 

 ploying the distinctive characters in fishes, that such great con-r > 

 fusion and contradictions prevail as were lately pointed out bjTii'; 

 Mr. Yarrell, in the fourteenth number of the Zoological Journal, 

 regarding the differences existing between the shad and white- ; 

 bait, which, it appears, had been confounded by one or two of 



