during their Groioth and Development. 119 



is in the highest degree a pelagic fish, the young of which, 

 easily recognized and impossible to confound with any others, 

 are captured everywhere between the tropics, and even beyond 

 them, especially the youngest forms. It is therefore not diffi- 

 cult to obtain a series of all the successive stages of this genus. 

 Nevertheless, in this great accumulation of more or less juve- 

 nile forms derived from very widely separated parts of the 

 great seas of the globe, I have been unable to distingaish more 

 than one species, and have come to the conclusion that, 

 properly speaking, we only know a single species belonging 

 to this genus, namely the pelagic and essentially cosmopolitan 

 species known under the name of S. saurus or 8. Camperii. 

 I must, however, make an exception in favour of 8. hrevi- 

 rostris of California, a very distinct species described by 

 M. Peters, which is distinguished by an excessive abridge- 

 ment of the two jaws, a peculiarity to which we find an ana- 

 logue in the young of 8. saurus in a certain stage of evolution. A 

 critical examination of the characters indicated for the other 

 species of 8comheresox also seems to show that they do not 

 rest upon a very solid basis ; but I must leave it to the ichthyo- 

 logists of the shores of the Mediterranean to elucidate 

 from this point of view the case of 8. Rondeletii and its 

 relationship to 8. saurus of the Atlantic. The anatomical 

 character upon which its separation as a distinct species is 

 founded has not, so far as I know, been verified since it was 

 established by M. Valenciennes ; hence it does not appear to 

 have any real foundation ; and the 8comberesoces from the 

 Mediterranean that I have examined possessed a swim-bladder 

 like those of the ocean. 



Another eminently pelagic form of this group is Eulepto- 

 rJiamphus longirostris. There is therefore a certain proba- 

 bility in favour of the opinion that all the different species 

 which have been established in this genus from individuals 

 fished in the two great oceans at points very distant from one 

 another are only representatives of a single pelagic and cos- 

 mopolitan species ; but for the more satisfactory verification 

 of this supposition it would be necessary to have at command 

 more considerable materials than any museum at present 

 possesses. 



16. POMACANTHUS; HOLACANTHUS ; Ch^TODON ; 



Tholichthys ; Ephippus. 



On the shores of the Antilles there live two species of 

 Pomacanthus which are certainly distinguished at all ages by 

 positive and non-equivocal characters, but which in habit. 



